Check out this blog post I found.
Not only are there hardware recommendations, but there's also some tricks that you can use if your current usb stick does not have a write protect switch.
Those of you counting on the little tab on a SD card for write-protection will want to read this too.
Personally, I'm using a 8GB Kanguru FlashBlu 2 that I got from amazon for about $27. It seems pretty fast (for someone who has not done any speed tests and has always bought whatever cheap flash drive was on sale at office depot in the past). My only complaints would be that I wish the key-chain mounting hole was a bit more robust-looking, and I wish the switch was a bit larger and had better tactile feedback. The switch appears to be like something that one might find on a PCB and might have a spec of maybe 100 cycles or something.