System Tray Audio Device Switcher
I actively use both a Bluetooth headset (a Logitech® Mobile Pro™) and a Rode NT1 microphone on my computer. The headset I use for making and taking Skype calls and listening to podcasts at home, while the microphone I use for narrating video tutorials and recording podcasts. The problem is, switching between these audio sources is a minor pain (which becomes a major pain through repitition), requiring a trip to the Control Panel every time.
Thankfully, I've found this free utility called, in various places, System Tray Audio Device Switcher, SysADS, SADS, and System Tray Audio Device Manager. It lives in my Windows system tray and allows me to select my playback and recording device with just a couple of clicks. The program hasn't been updated since its release in 2003, but it works on Windows XP SP2 just fine (I'm not holding my breath that it'll work quite so well in Vista, however).
Even with this utility, most Windows programs can't switch audio devices while running. Windows Media Player, for example, will latch onto the selected playback device when it starts up, and will continue outputting to it even if you switch devices while it's running. More flexible programs like Skype do allow you to switch devices at any time, but only by overriding the system default device in the program's own settings.
In short, this utility does save me the trip to the Control Panel to change audio devices, but I still need to restart any audio programs I may have already open in order for the switch to affect them.
Here's hoping things get better, not worse, in Vista.