acbToggleBT is a lightweight utility to play sound over your bluetooth headset.
If you have a paired headset, running this program will instantly send all audio through the headset. Run the program again to stop sending sound to the headset.
Assign this program to a hardware key and route sound to your headset with the touch of a button.
If you're familiar with BTAudio, this program does the same thing. The advantage is that this application is not based on the .Net Compact Framework, so instead of taking a few seconds to load, it's immediate. Also, it has no UI, so you don't have to do anything other than launch the program.