To anyone using the '-fixed' themes (orange-fresh-fixed, etc.), sorry! I just renamed the whole set and broke your site's look and feel. My apologies. The experimental phase of these themes is now over and they are ready for beta use.
Perhaps we should apply version numbering to themes to let people know how stable they are. These themes would now be in rc-1.
Gabrys pointed out that the fixed 950px themes were not ideal for an open source project, where it's necessary to put a lot of information onto a page. Unlike a blog, where the goal is to get the most hits with the least possible writing…:-)
So I looked into it and found out how to make multiple variations for the same external theme. If you use http://themes.wdfiles.com/local--code/orange-juice as your external theme, you get the fixed-width variation. If you use http://themes.wdfiles.com/local--code/orange-juice/3 you get a wider variation that stretches up to 1200 pixels.
Here is a theme chooser that shows the new URLs.