If your interested on what the 'average surfer' is using you should check out this page: http://www.thecounter.com/stats/2002/November/res.php
It's basically the accumulated logs for all the visitors who accessed a 'thecounter.com' counter in the month of Nov'02.
There were 348 million people who accessed the counter that month so you can assume it's a pretty accurate view on the resolutions used out there - and I bet your might be a little surprised at the top one
Of course that's just the average surfer... skinners, graphic artists and gamers are bound to use higher resolutions, but still it gives you a good idea of the 'real' picture out there - instead of just people who participate in polls and messageboards