As TJ191 mentioned in a previous theme song thread, the new WAB theme is "Calling All Friends" by Low Star. The complete song is available for download on the band's MySpace page...
However, the edited version of the song that the show uses isn't actually part of the full song; it's tweaked a bit. I had been unable to find it anywhere for download, but ABC just made my day by adding "Brian" to the roster of programs available for viewing online.
So I fired up my sound recording program, ripped the show's edit of the song from the streaming broadcast, converted it to mp3 format, and uploaded it to the web so any fans of the show who want it can download it for free. Just click the link below, then follow the instructions for downloading the file.
Please note that the sound quality is only as good as the stream's audio, but it's actually quite good with just a little background fuzz. Enjoy!