Nvidia has just launched the GeForce 8800GT, and by all accounts it hits the price/performance sweet spot. Basically the 8800GT will cost $200-$250, but it handily outperforms the 8800GTS cards (which cost $300-$400) and does almost as well as the 8800GTX ($375+).
For those of you with money to burn, apparently two 8800GTs in SLI configuration will outperform a single 8800GTX 640MB (and 2 GTs is cheaper).
Anyway, prices are a bit high right now because the cards were just released this week, but I am definitely getting one of these babies in a few weeks when it's like $230.
Here's some reviews/benchmarks:
http://enthusiast.hardocp.com/article.html?art=MTQxMCwxLCxoZW50aHVzaWFzdA==
http://www.tomshardware.com/2007/10/29/geforce_8800_gt/
http://www.techreport.com/articles.x/13479
Edit: corrected an error. Originally I said 2 8800GTs would beat 1 Ultra, but they won't. They'll beat 1 8800GTX 640MB.

Not to mention the great benefits in Crysis and Bioshock and whatever else comes out in the next six months.