Link to $100 bonus (link dead)
To qualify to have $100 deposited into your account, you will need to open an eligible Fidelity account and fund it with at least $10,000. This offer is available for new households only.
Existing customers okay as well: "Existing Fidelity Brokerage customers must provide the information requested above and then deposit or transfer in at least $10,000 in assets to their individual or joint Fidelity Account."

Link to UA mileage offer

Link to AA mileage offer
"Open a new, non-retirement Fidelity Brokerage Account today, and you'll not only be taking steps towards achieving your financial goals — you'll be up to 25,000 American Airlines AAdvantage® miles closer to your dream vacation. Offer valid for new customers only."

Fidelity mySmart Checking
Link
This is a seperate FDIC checking worth a look by anyone doing this deal. It has ATM Rebates, no min, no fees, 3.5%APY. The checking can be linked to the Money Market account and any withdrawal of the checking can trigger a sell of the money market.

"Double-dipping?"
If you qualify for both deals, you can get both the $100 bonus and the airline miles. Just register for both before opening your account. We think it tracks you by your SSN.

What is a "core" account?
"Core" is Fidelity's term for a sweep money market. Unvested cash is swept in at the end of each day. You normally use these funds to purchsae investments (including other money market funds), but if you're lazy, you can just leave funds in the core money market as an investment.

How do I change my core account?
When creating a new account you are asked which core account you would like. You can select several different choices. The default is FCASH, which is a low-yielding taxable cash sweep. This is a crappy option. It's generally superior to select one of the tax-free municipal fund sweeps. Not only do they have a higher yield, but they are usually tax-free.

You can change this acount at any time. However, don't waste your time looking around the website for how to change this; you can't do this on the website. You must call customer service OR use the online chat feature found via Customer Service > Contact Us

If your intention is to hold a bunch of money in a money market for a while, you can get slightly higher yields by buying a "transaction-based" money market fund. These are funds that you have to intentionally make "buy" and "sell" transactions to get into. A popular one is FSLXX, because it usually has the highest yield amongts taxable MMFs.

Select Money Market Portfolio 85 FSLXX
7-day avg yield (slightly lower than APY, does not reflect compounding):
3.73% as of 10/31/05
3.99% as of 12/21/05
4.57% as of 04/04/06
4.90% as of 06/28/06
5.16% as of 08/31/06
5.34% as of 09/17/07
5.26% as of 10/12/07
4.90% as of 11/10/07
4.36% as of 01/29/08
3.93% as of 02/15/08
2.79% as of 05/03/08

If you are subject to AMT, you should consider the following:
Fidelity Tax-Free Money Market (FMOXX) - 5K min. investment
2.77%(Tax Equivalent Yield 4.26%) as of 01/08/2008

If you are subject to AMT and live in California, you should consider the following:
Fidelity California AMT Tax-Free Money Market Fund (FSPXX) - 25k min. investment
2.90%(Tax Equivalent Yield 4.97%) as of 01/08/2008

Is this FDIC insured?
No. Money markets have an extremely small chance of losing money, but are not insured. Note that Fidelity can sell "brokered CDs", which really are FDIC insured. You can also buy US Treasury bills, notes, and bonds, either individually or in mutual funds. The underlying notes are backed by the full faith and credit of the US government.

Q: WHAT'S THE DEAL WITH CHECKWRITING OUT OF A MONEY MARKET?

Some people want to keep their money in a higher-yielding transaction-based mutual funds, like FSLXX, rather than the core. The question is, what happens if they to a withdrawal (check or ACH, doesn't matter), and there is not enough money in the core account? Well, here is what happens:

1) Funds are first deducted from the core account.
2) If your account has margin, the margin is used to clear the withdrawal.
3) If you do not have margin, or if you run out of margin, then any transaction-based money markets are sold to cover the difference*. There is no limit or fee for this.
4) Other stocks, bonds, or mutual fund holdings, are never automatically sold to cover a transaction, so the transaction would bounce.

* Even though the FSLXX details page says "no checkwriting", that's only for mutual funds purchased directly. We're talking about a brokerage account here, and the money market fund can be auto-sold within a brokerage account, with no fees or limits.

Fidelity Direct Deposit page
Fidelity Direct Debit page

The Fidelity routing number: 101205681

Update 01/30/2008
Bonus offer for each account is DEAD. Now they have added a clause “one per house hold”. $100 bonus per customer or SSN. No multi dipping.

Update 02/01/2008 from the website fine print.
1 Offer rules and restrictions to receive $100:

Offer valid for individual or joint Fidelity accounts, personal trust accounts, and business accounts that select the taxable cash account as its core account. Offer is not valid for retirement accounts (including IRA, Roth IRA, Rollover IRA, Self-Employed IRA, SEP and SIMPLE, 401(k), 403(b), etc.), some fiduciary accounts (including custodial accounts, stock plan service accounts, estate accounts, etc.), 529 accounts, and accounts managed by Strategic Advisers, Inc.