I'm in love with my TI-84+ Silver... but $20 of it was just for "pretty" wink The prices are generally fairly comparable though with the 84 just about $20-30 more than the 83... The functions are close enough that so far I can use a TI-83 manual for the 84+ without a hiccup. So I think if you find one cheap you can go either way. Definitely a TI though... I'm sure there are other ones, but it appears to be The Standard.

Staples seems to have a TI-83+ for $90 right now, and a TI-84+ for $110

Erica