Interested in benefits that are not cash/points/miles? See this thread for the unique non-cash benefits that different credit cards have

Balance Transfers
CreditCards.com balance transfer cards section[link]
Best Balance Transfer Credit Cards [fw thread]
[Obviously spammy links removed]

Bonuses
Credit card sign-up bonuses [fw thread] - sorted by value, bank name and expiration date, $12,000 in total

Calculators
Credit Card Tune-Up: A utility to find the best reward credit card or combination of cards for your categorical spending profile is this rewards calculator [link], [fw thread]
Credit Card Tune-Up for Canadian rewards cards [link], [fw thread]

Rebates
Reward credit cards sorted by the value of annual rebate/gift card rewards for an average US family. [fw thread],[link]

Gas
5% Associated Bank Cash Rebate Card - $300/year Cash Back limit - phone application only: 1-877-577-9485
4% Costco TrueEarnings American Express Business Card link (4% for gasoline, for annual purchases up to $6,000 meaning up to $240 CashBack per year)
3% Costco TrueEarnings American Express Card [link] (3% for gasoline, for annual gasoline purchases of up to $3,000 (1% thereafter) meaning 3% up to $90 CashBack each year)
3% Chase Sheetz Mastercard: 3% Sheetz purchases, 2% grocery&travel, 1% general (10% Sheetz purchases first 90 days)
3% Citi Professional Cash Card: [link] 3% Cash Back for 12 months, 1% thereafter)
3% Chase Professional MasterCard: (Business card, 3% @ Restaurants, Office Supplies Stores, Gas, Home Improvement stores, Building Supplies Stores)link rewards details link
3% American Express SimplyCash Business Card (also 5% on office supplies, telecom) [link], [cardoffers link]
3% Chase Freedom Card: [fw thread] (You get unlimited 1% ca$h back on everything, then 2% for the first $600 on gas/groceries/fast food each month (max $12 on rewards that qualify for 2%)
up to 5% American Express Blue Cash: 5% ca$h back on gas/groc/drugstores after you have spent $6,500 for the year
5% Chase BP Visa: 5% at BP service stations, plus 2% dining & travel (incl. airfare), 1% general. Double rewards (10%/4%/2%) in first 3 months FW thread
5% Barclay's Sinclair Platinum Mastercard: 5% at Sinclair stations, 1% general
5% Discover Open Road: 5% Ca$h back on first $1,200 in annual gas & auto maintenance purchases. Effective October 1, 2007, 5% Ca$h back on first $100 in gas & auto maintenance purchases each month - up to $1,200 each year [link]
5% Penfed Visa Platinum Gas Cash Rewards Card: [fw thread] [link]
up to 8% Lukoil Platinum MasterCard: up to 8% at Luk Oil and Getty gas stations http://www.lukoilmastercard.com/
up to 10% Washington Mutual Platinum MasterCard: (for 1st 6 months/up to 5% thereafter) [link], [fw thread]

General Purpose
3% Citi Platinum American Express: Up to 150k TYP (TYP worth approx 1 cent per point), for 24 months (5% supermarkets, drug stores, gas, 3% for everyting else). $125 fee waived first year. [Link]
1% Chase Freedom: [fw thread]
1.25% Penfed Visa Platinum Gas Cash Rewards Card: no caps, no tiers, monthly credits, plus 5% gas and 2% groceries ca$h back [fw thread]
1.25% Capital One No Hassle Rewards Card: 1% ca$h back plus annual .25% bonus
1.33% American Express Blue Sky: for each $7500 spent, get $100 toward any travel expense. No restrictions on where you can earn points.
1.4% Emigrant Direct Platinum MasterCard: Requires $10K balance at Emigrant Direct [link]
up to 1.5% American Express Blue Cash: 1.25% ca$h back on everything after you have spent $6,500 for the year [fw thread]
1.5% Fidelity Investment Rewards Visa Signature Card: 1.5% flat ca$h back (2% after $15k annual spending), requires Fidelity account [link]
up to 2% Citi Driver's Edge: 1% TY points plus the chance to double with 1 point/mile you drive [link], [fw thread] - *No Longer Being Offered*
up to 2% Citi Premier Pass: 1% TY points plus the chance to double with 1 point/3 miles you fly
up to 2% Citi Premier Pass Elite: 1% TY points plus the chance to double with 1 point/1 mile you fly ($75 annual fee) [link], [fw thread]
up to 2% Travel0city Rewards MasterCard: up to 2% ca$h back, 4% on purchases at Travel0city ($29 annual fee) [fw thread]
up to 2% Sam's Club Discover Card: (accepted everywhere Discover is accepted), 2% on purchases between $10,000 and $1 million per year, lower tiers before that [SamsClub]
2% Schwab Bank Invest First Visa: Flat 2% cash back, credited monthly, requires Schwab account [link], [fw thread]
2% Fidelity Retirement Rewards American Express Card: requires Fidelity account [link], [FW thread]
2% HSBC / Orchard Bank Premium Platinum MasterCard (annual fee for some, mostly targeted, but you might be converted to the 2% program when you try to cancel). See thread for important details.) FW thread

Groceries
5% Associated Bank Cash Rebate Card - $300/year Cash Back limit - phone application only: 1-877-577-9485
3% Chase Freedom Card: [fw thread] (You get unlimited 1% ca$h back on everything, then 2% for the first $600 on gas/groceries/fast food each month (max $12 on rewards that qualify for 2%)
3%: Bank of America Worldpoints Platinum plus MasterCard: 3% on Gas and Groceries Apply
5%: Citibank Dividend Select: for new customers for the first 6 months, 2% afterwards [fw thread]
up to 5%: Am.Ex Blue Cash: 5% ca$h back on gas/groc/drugstores after you have spent $6,500 for the year [fw thread]
up to 5%: Washington Mutual Platinum MasterCard: 5% ca$h back on gas/groc/drugstores after you have spent $4,000 for the year [link], [fw thread]

Home Improvement
3% Chase Professional MasterCard (3% @ Restaurants, Office Supplies Stores, Gas, Home Improvement stores, Building Supplies Stores)

Hotel Cards
3.75% (3%) Chase Freedom Business Card
hilton HHonors by Citi [link] or Am.Ex [link]
Am.Ex Starwood: [am.ex link]; or Business [cardoffers link] / Personal [cardoffers link]
Marriott Rewards Visa Signature [Link] 20K points w/ first purchase free night stay, $30 annual fee (waived 1st year)

Office Supplies
3% Citi Professional [link]
3.75% (3%) Chase Freedom Business Card
3% Chase Professional MasterCard (3% @ Restaurants, Office Supplies Stores, Gas, Home Improvement stores, Building Supplies Stores)
5% Am.Ex SimplyCashSM Business Card (also 3% on gas, 5% on telecom) [link], [cardoffers link]

Pharmacy/Drugstores
5% Associated Bank Cash Rebate Card - $300/year Cash Back limit - phone application only: 1-877-577-9485
2%: Citi Divdend Platinum Select
up to 5%: Am.Ex Blue Cash: 5% ca$h back on gas/groc/drugstores after you have spent $6,500 for the year [fw thread]
up to 5%: Washington Mutual Platinum MasterCard: 5% ca$h back on gas/groc/drugstores after you have spent $4,000 for the year [link], [fw thread]

Phone
5% Am.Ex SimplyCashSM Business Card (also 3% on gas, 5% on telecom) [link], [cardoffers link]

Public Transportation & Parking
Citi Premier Pass Elite: 2 Thankyou points/$ plus double with flight miles [link], [fw thread]

Restaurant
3% Am.Ex Costco card [link]
3% Citi Professional Cash Card [link]
3% Chase Professional
3% Chase Freedom Card (Fast food only): [fw thread] (You get unlimited 1% ca$h back on everything, then 2% for the first $600 on gas/groceries/fast food each month (max $12 on rewards that qualify for 2%)
5 Thank You Network points (currently 3.125% if redeeming Cash Back) Citi Forward Card
5 Thank You Network points (currently 3.125% if redeeming Cash Back)(student only) [link], [fw thread]

STORE SPECIFIC CARDS (Thanks to those who submitted these cards!)
TJX Rewards Mastercard 5% rebate at T.J.Maxx, Marshalls, HomeGoods and A.J.Wright, 1% elsewhere
Shell Gas MasterCard- 5% rebates @ Shell and Jiffy Lube
Marathon Gas MC- 10% @ Marathon for 60 days 2% elsewhere, then 5% @ Marathon. 1% elsewhere.
Hess Gas Visa- 10% @ Hess for 90 days, then 5%. 1% elsewhere.
Banana Republic Card 5% at Banana, Gap, & Old Navy. Can't be used anywhere else.
Hooters Mastercard- 5 points w/ Hooters, 1 point elsewhere.
Continental Airlines MC 5% off CO fares for 1 year, $65 annual fee.
AAA Rewards Visa Look on your region's site for current offer (5% on gas, limited to 2% of your total net purchases that billing cycle)
Choice Hotels Visa Earn 15 points per $ at Sleep, Comfort, Quality, Clarion, & Mainstay. 2 points elsewhere.
Marriott Rewards Visa Signature 5 points at Marriott, 2 for travel, 1 elsewhere.
REI Visa Up to 10% back on REI, 1% elsewhere.
BP Rewards Visa double rebates for 2 months, then 5% @ BP, 2% Dining, Airline, Car Rental, and lodging, 1% elsewhere.
Mercedes Benz Visa 5 pt/$ spent @ M.B. dealerships and on merchandise.
Sinclair MC by Juniper For 60 days you'll earn 7% at Sinclair, 2% elsewhere and then 5%/1%. Not bad!
Gymboree Visa by US Bank Save 5% at Gymboree (Kid's Clothing) and 1% elsewhere. $10 sign up bonus
Moved- AT&T Universal MC 10% on AT&T/Cingular Purchases for 12 months then 5%

Student
Calculator for Student cards: A utility to find the best reward card or combination of cards for a college student's categorical spending profile [link], [fw thread]
Citi mtvU: 5 Thank You Network points (currently 3.125% if redeeming ca$h back) restaurants, bookstores (Amaz0n.com!), movies, movie rentals [link], [fw thread]

Travel Purchases
2% Am.Ex Costco [link]
1 TYP/$ plus 1 TYP/mile flown (PremierPass Elite [fw thread 1] [fw thread 2]) or 1 TYP/3 miles flown (PremierPass)
Chase BP Visa: 5% at BP service stations, plus 2% dining & travel (incl. airfare), 1% general. Double rewards (10%/4%/2%) in first 3 months FW thread
Citi Professional Card - 3% on Rental cars (with free Travel insurance and PRIMARY rental car insurance)

USPS / United States Postal Service
None

Utilities, Cable
2% Citi Dividend Platinum Select (excludes phone)
6% Citi Home Rebate - (for 1st 12 months) payable towards a mortgage. Telecom Services. Computer Network / Information Services. Cable, Satellite and other Pay TV and Radio Services, Utilities; 1% on everything else. [link]

Business
Calculator for Business cards: A utility to find the best reward card or combination of cards for a business's categorical spending profile [link], [fw thread]
Chase Professional MasterCard (3% @ Restaurants, Office Supplies Stores, Gas, Home Improvement stores, Building Supplies Stores)

Car Purchase/Repair
3% Chase Subaru ($500 annual limit, 4-yr expiration period)

Department Stores
3% Capital One

Movies, Books, Music
5 TYP (3.125% if redeeming ca$h back) Citi Forward Card
5 TYP (3.125% if redeeming ca$h back) Citi MTVU Card