I'm working on a small C# system tray app that allows you to switch between default sound devices a little bit quicker than going through the sound control panel...
If you are interested, here's a link to a zip file that has the 3 files needed to run the app - the app itself, a DLL to control audio devices and an EXE to make the changes take affect - http://dl.dropbox.com/u/1094970/AudioSwapper.zip.
There's no installer, just unzip the files into a folder and run AudioSwapper.exe. You'll see a new speaker icon in the system tray, just right click and choose the device you want to use or to get to the various options.
I'm looking for bugs in what's there now, not necessarily any feature requests, so please limit feedback to problems that you are running into and I'll see if I can get them fixed.