 Since quitting Seether, Callahan has spent time working with children in a Philadelphia music school called the Music Training Center.He has also played and toured with Metallica, Evanescence, Audioslave, Green Day, Staind, Breaking Benjamin, Slipknot, 3 Doors Down, Shinedown, Def Leppard, and Lionel Richie.In the past, Callahan has made several television appearances which have included MTV, "The David Letterman Show", "The Tonight Show with Jay Leno", "Last Call with Carson Daly", and "Jimmy Kimmel Live!