In my experience (and indeed my stats would confirm that) whilst there are still some people out there using 800 x 600, the majority favour 1024 x 768 or above.
However, as Bill mentions, those using a screen 1024 wide will be unlikely to have 1024 pixels at their disposal. I tend to aim for 850 x 900 wide on most things I've done lately. I think that most people will survive that without a horizontal scrollbar.
Bookmarks