I am trying to create a menu with dynamic width, much like here:
http://computers.pricegrabber.com/

(You'll notice X items appear under the last "More" item depending on browser width)

I've gotten everything working just fine, but my problem is that everything shows up immediately and then it will not resize accordingly until the page has loaded and it looks fine. With their website though, I do not notice ANY jump AT ALL, yet all the code for each menu item is in there and there is no class for them to be hidden or anything.

Any ideas how I can avoid the initial "jump" upon page load? I can't figure out how it is so smooth on their site...

Are you using the onload event? If so, you should probably look into using something that fires earlier. jQuery has $(document)ready(), and YUI has a number of similar events.

(I should probably add that I only looked at the site briefly and didn't really figure out what it was doing on startup. So there may be something else clever you can do instead.)