Danny recommended this quality podcast and I'm hooked. After listening to the latest few episodes, I'm now starting from the beginning and catching up on the (non-) adventures of Commander Major Alastair Q. Bastidious and First Lieutenant Rutuger G. Phooneybaum. Their improv and timing is excellent and I love the subtle use of sound effects... your imagination fills in the gaps and you can visualize everything. Here's a description from their site:

"The Mustache Rangers are a podcast and improv comedy team from Minneapolis, Minnesota. Their performances and podcasts are best described as a cross between Buck Rogers, Curb Your Enthusiasm, and Samuel Beckett."