There’s a lot of web standards-based css tab menus out there, but I have to say I’m pleased with this one by Ian Andolina because it dropped into my application and worked right away. It took me just a couple of minutes to change the font and coloring, but other than that, it was a breeze.
Though I had a little trouble with Adam Kalsey’s own tabbed menu, his page lists several alternatives (which is where I found Ian’s above).