Matt Besser was one of the four co-founders (along with Amy Poehler) of the Upright Citizen's Brigade, which not only had a Comedy Central show, but was the first improv comedy theater in NYC, and included folks like Adam McKay (Anchorman, Talladega Nights, etc.), Armando Diaz. Before that he trained at iO (Chicago) with Charna Halpern and Del Close, and was part of the improv group The Family. Matt also has done stand up comedy (longer than improv!) and has a podcast called Improv For Humans. You can download his comedy albums for just $1.99 each here. Also, he just finished co-writing The Upright Citizens Brigade Comedy improvisation Manual.