If you're going for a fixed width design, then designing for 1024 width is relatively safe these days. Lots of people are moving that way, but for widest support you still need to consider those on lower resolution.
The current trend for fixed 1024 designs seems to be to either place some less important content on the right-hand side column [doesn't matter if it's offscreen], or implement the right-hand content so it reflows down to the bottom of the page on lower resolutions [i.e. a fluid layout within a fixed width].