I just got a Galaxy SIII and have been looking for inexpensive case options. Stumbled across this thread from a while back, and while these are a bit more expensive, the coupon code deducts around 60% from all GSIII accessories. It appears that the $25 threshold for free super-saver shipping is based on pre-coupon prices, which is nice, but when I was checking out, I saw an offer for a free month of Amazon Prime. I've had a couple of free trials, but the last one was probably 2-3 years ago, so I imagine this is highly YMMV for those who are more diligent about such things. Long story short, I got 2 cases with 2-day shipping (and Prime for my upcoming Black Friday binge) for $15.
If you do a search for "Link for the lazy" you'll get everything that's coupon eligible:
There are a bunch of others that could work out nicely, especially with the free Prime on most of them. If you can't get it though, the $25 threshold for FSSS is based on full prices, so if you want 2 or 3 cases, that would be an option as well.
Good luck, and happy hunting.
I love the phone, but given the size and lack of "grippiness" of the phone, I wanted some sort of case.