I just installed the PowerCommands 1.1 for Visual Studio 2008. This is a set of extensions to the VS 2008 IDE that provide some additional functionality. The available commands are listed here. The Collapse Projects command sounds pretty basic, but it's something I've always wanted and it's great for large solutions.
The best part of PowerCommands? You get the source code, which would be handy if you ever want to write your own VS extension.