depends on what you would like to spend and how much you want to game. you can get a geforce 3 ti200 for $40 or $30 if you look around; shouldn't be too hard. those cards hold themselves very well, and have only began to show real weaknesses in the newer games like farcry and doom3. if you're a gamer like me though, that's unacceptable
lol. a 9800 pro can be had for real cheap right now because so many people are getting rid of their lastgen cards to buy new ones. you can buy a 9800 pro here
for $100. of course, read what the guy has posted about it to make sure you don't think you're getting something your not. only an example, not suggesting you actually go for this particular deal.
you can also find gf4 cards for right around $75... not a bad deal, they run well. a 9600xt could be had for a fair price, those are good. don't go for the 9500np, they can be modified to a 9700 pro, but people have caught on to this and they cost about the same now anyway, so it makes no difference.
also a good card right now is the 5900xt. it's value is great, and used i'd say you could find one for a great price. brand new they wont break you, but the 6600gt would be a much better choice if you were going to go the new route.
without regard to price, i would say that the best card you can get right now is probably the 6800gt as they overclock well, or the x800pro vivo. these bad boys (the x800pro vivo) can be flashed to an x800 XT PE. not a bad deal at all
all around in the video card good things are happening right now. competition is nice and healthy, and the performance of video cards from last generation to this generation has doubled... along with pricing being drastically lower compared to other generations.
really, if you get any next-gen card, you'll be hard pressed to go wrong. everything that's out this generation is just excellent.