Side project

In music, a side project is a project undertaken by one or more people already known for their involvement in another band. It can also be an artist or a band temporarily switching to a different style. Usually these projects emphasize a different aspect of that person's or that band's musical interests that they feel they cannot explore within the boundaries established by their main project.

Side projects can later become full-time endeavours, but should not be confused with quitting a band for a solo career or another band.

List of side projects
Often various artists can start up multiple side projects, undertaking one at a certain point in time before starting another, or sometimes at the same time. Within a band, multiple members of a band can participate in the same side project, or just one can start one up.

Note: Everything here is sorted by artist.

Avenged Sevenfold

 * Pinkly Smooth

David Bowie

 * Tin Machine

Phil Collins

 * The Phil Collins Big Band

Deep Purple

 * Gillan & Glover

Disturbed

 * Device
 * Fight or Flight

The Doors

 * Manzarek-Krieger

Jerry Garcia

 * Black Mountain Boys
 * Jerry Garcia Acoustic Band
 * Jerry Garcia Band
 * Legion of Mary

Ian Gillan

 * Gillan
 * Ian Gillan Band

Grateful Dead

 * The Dead
 * Dead & Company
 * Kingfish
 * New Riders of the Purple Sage (started out as a side project but eventually grew to more or less become its own entity.)
 * The Other Ones

Green Day

 * Foxboro Hot Tubs
 * The Network

Dave Grohl

 * Probot

Rob Halford

 * 2wo
 * Fight
 * Halford

Jefferson Airplane

 * Hot Tuna (started out as a Jefferson Airplane side project but grew to become its own entity.)
 * KBC Band

Led Zeppelin

 * The Honeydrippers
 * Page & Plant

Alex Lifeson

 * Victor

Dave Matthews

 * Dave Matthews & Friends
 * Dave Matthews and Tim Reynolds

Metallica

 * Spastik Children

Panic! at the Disco

 * The Young Veins

Robert Plant

 * Robert Plant and the Band of Joy

Queens of the Stone Age

 * Eagles of Death Metal

R.E.M.

 * Hindu Love Gods (with Warren Zevon)

Santana

 * Abraxas Pool

Slash

 * Slash's Blues Ball
 * Slash's Snakepit

Izzy Stradlin

 * Izzy Stradlin and the Ju Ju Hounds

Talking Heads

 * Tom Tom Club

Tenacious D

 * Kyle Gass Band

Pete Wentz

 * Black Cards

Zakk Wylde

 * Pride & Glory
 * Zakk Sabbath

Yes

 * Conspiracy