Meebo sidebar for Flock
Meebo is great. It's full of AJAX-y goodness, connects through port 80 (which is useful when you're on a network that blocks standard IM ports), and works with the big 4 IM protocols. The only real issue I have with it is the fact that opening a new tab or new window hides my buddy list. Some intrepid soul has hacked up an extension for Flock which places Meebo in a persistent sidebar frame that stays visible as you browse. I normally just use Adium and OmniWeb, but the school network won't allow Adium to connect, so this looks like the perfect solution to my problem. As with flock, this extension is available for Windows, Mac, and Linux.