Impact Blue Some fantastic Flash design here. Check out the pull down menues with transparency.

Tristream These guys have done some good work. Check out the logos.

Pacific Edge I like how they used a lot of color to highlight where the primary navigation is found. If their software is as good looking as the web site, it might be interesting.

phpBB This site reminds me of what we were all trying to do 5 years ago with a simple site. This design style should be replicated across the OS world.