I'm not sure I've actually seen any floating plants from PetSmart but I haven't been there in a while.
Here's a website that will help you determine plant species from the amazong: www.plantgeek.net and just go to the Plant Guide and search under different thigns that you are looking for.
Salvinia is a cool floater. not sure if its amazon but it looks good and doesnt grow out of control like duckweed. i saw some good deals on it on aquabid so you should definitely look there.
I got a Rena XP2 from www.bigalsonline.com and it's free shipping over $75. I'd get the XP3 if I were you, a few more dollars but worth it if you're thinking about getting Rena Filstar XPs.