Well that depends, if you are clumsy and drop stuff, you're gonna want to go with a heavier case, if you take good care of it, go with one of these:
http://www.bestskinsever.com/servlet/StoreFront - look great, tough material
http://www.bodyguardz.com/ - also looks great and is very tough
http://www.zagg.com/ - more like a covering but its military grade - would suggest this one if you want max protection without losing sexiness
or obviously a leather case, but i had one of these when i first got my touch, and dust got all over it but they look good. plus it wasnt covered completely for scratches
then if your a klutz, lol , get:
http://vibevault.com/xcart/product.php?productid=16203&cat=0&page=1- still looks okay imo.
Oh and btw ipod touch second gen is rumoured to be coming out late this year, but i doubt you can wait that long, i wouldn't