==Puscifer==
[[Maynard James Keenan]]'s side project, Puscifer, has 2 officially released songs: "REV 22:20" and "The Undertaker (Renholdër Mix)" on the ''Underworld'' soundtracks. A remix of the former, "REV 22:20 (REV 4:20 Mix)" by [[Charlie Clouser]], was on the ''Saw II'' soundtrack. Further work is in progress with [[Danny Lohner]], Lustmord, and others.
==Tapeworm==
After The Downward Spiral tours in 1996, [[Danny Lohner]] and [[Charlie Clouser]] approached Trent with music ideas that Trent felt did not fit in with his vision of the band, but instead agreed to collaborate and work on the material as a side project, with each member having equal say in decisions. The band eventually became a supergroup of sorts including, among others, Maynard James Keenan (Tool, A Perfect Circle), Page Hamilton (Helmet), and Phil Anselmo (Pantera). Over time, the band began to break down, partly due to label issues and partly due to Trent's lack of interest in the project and announced the band was dead in 2004. However, it has been rumored that the tracks of Maynard's Puscifer project are renamed and reworked versions of the Tapeworm tracks.
==Tweaker==