The theme song heard at the beginning of 'Psych' every week is entitled, "I Know, You Know" and is performed by a band out of Orange County called The Friendly Indians.  What makes this particular theme song interesting is that the frontman of the band performing is the show's creator and executive producer Steve Franks.  For more information on the band, please visit their website at: http://www.friendlyindians.com/

And to download the theme song, right-click and save as.