Dave Lombardo (drummer: 1982-1986, 1987-1992, 2001-present): After leaving Slayer twice to form the band Grip Inc. and pursue projects with Finnish band Apocalyptica and Fantómas (fronted by former Faith No More singer Mike Patton), Lombardo got back with Slayer for good, so far on its 2001 God Hates Us All tour.
Tony Scaglione (drummer for a brief time in 1986): Recruited by Slayer when he was only 18, Scaglione filled in for the last leg of the Reign in Blood tour, then was dismissed when the tour ended and Lombardo rejoined the group. Scaglione later drummed for bands M.O.D., Raging Slab, Sheer Terror, and Whiplash. He was also in the Phoenix-based bands Cause for Alarm and North Side Kings with singer Danny Marianino (better known around Phoenix as "that guy who knocked out Glenn Danzig"). Last we heard, Scaglione was living in Phoenix with his wife and drumming for several "projects."
Paul Bostaph (drummer: 1992-1996, 1997-2001): Bostaph had already drummed for a fairly popular thrash metal band, Forbidden, when Slayer guitarist Kerry King asked him to join in '92. When Bostaph left the band in '96, it was to join a universally ignored side project called The Truth About Seafood. When he left again in 2001, he claimed he had a crippling injury, then quickly joined the Bay Area band Systematic. He currently drums for Exodus.
Jon Dette (drummer: 1996-1997): Dette joined the band after Bostaph's first departure, and the reason for his dismissal from Slayer has never been clear. Slayer cited personal differences, Dette cited "political bullshit." He later played in Testament, Evildead, and Push. He now owns Digital Scream Studios in Carlsbad, California, and rumor has it he became a born-again Christian. Maybe that's the real reason he's not on Slayer's "Unholy Alliance: Preaching to the Perverted" tour.