You could go for a liquid layout, so that the containers on the page will move/resize when the browser window is resize. At my work (ntu.ac.uk), we originally had a liquid layout (as can be seen from the homepage), but we are now moving towards a fixed-width layout (see www.ntu.ac.uk/art). Our stats show that the majority of people (95%) are using screen resolutions of 1024x768 or above, so we have gone for a fixed width of around 960px (60ems) wide. Fixed width sites are generally easier to put together, and I would suggest that you can make the minimum width of your site 800px (50ems). Hope that helps.
RE: Thats brilliant, thanks. nt nt Global stats from thecounter.com for september:</p> http://www.thecounter.com/stats/2007/September/res.php </p> 50% using 1024x768, obviously this changes depending on the target market for your website.</p> If in doubt I would stick to about 750 wide, giving room for a scroll bar (at 800x600). </p>