Try to target 1024 as the minimum width. Try how it looks at 800, but don't bother too much making that work. At 800x600 almost none of the major websites are going to work, so people working at that resolution are going to have problems all the time anyway.
If you're going to go for a liquid layout, make sure that text doesn't get too wide, because when lines are too long, they become hard to read. That's the main reason why most websites have a fixed width.
