I've started using divs and CSS rather than tables. Makes it a hell of a lot easier
That affords me two main alternatives for layout
1) Fixed-width main div set at approx 754px centered on the page
2) 100% width with fixed-width side bar(s) totalling a maximum of 300px - which leaves a comfortable minimum of 450px for the content on smaller resolutions.
With option 2, if you use absolute positioning, you can get your main content read by the SEs before your left sidebar/nav menu content.
The only thing you have to worry about then, is that the DOC-TYPE declaration is set correctly for the page to look the same in all browsers. (Something that had me scratching my head for a couple of hours one day, wondering why IE wasn't laying out the divs correctly)