On my Ipod I have a playlist called Space: The Final Frontier, which contains mainly rock music with space-related titles and/or themes. Here's my list:

A Flock of Seagulls - Space Age Love Song
Arch Enemy - Starbreaker
B-52's - Hallucinating Pluto, Planet Claire, There's A Moon in the Sky (Called the Moon)
Beastie Boys - Intergalactic
Billy Thorpe - Children of the Sun
The Cramps - Rock on the Moon
David Bowie - Space Oddity, Ziggy Stardust (Bauhaus did a cover of this song that's almost spot on)
Dead Kennedys - One Way Ticket to Pluto
Def Leppard - Rocket
Derek Sherinian - Alien Hip Hop, Crab Nebulae, Space Foam
Devo - Space Girl Blues, Space Junk
DragonForce - Evening Star
Dream Theater - Under a Glass Moon
Duran Duran - Electric Barbarella, Planet Earth
Edguy - Rocket Ride
Elton John - Rocket Man
Gamma Ray - Anywhere in the Galaxy, Beyond the Black Hole, Men Martians & Machines, Somewhere Out in Space, Space Eater
The Gathering - Liberty Bell
Gojira - To Sirius
Joe Satriani - Surfing with the Alien
Liquid Tension Experiment - Chewbacca
Megadeth - Hangar 18
Metallica - Orion
Moby - We Are All Made of Stars
Monty Python - The Galaxy Song
Nightwish - Planet Hell
Pantera - Planet Caravan
Peter Schilling - Major Tom (Coming Home) (A recent cover of this song by Shiny Toy Guns is really good)
Pink Floyd - Astronomy Domine, Set the Controls for the Heart of the Sun
The Police - Walking on the Moon
Rush - Between Sun and Moon, Countdown, Cygnus X-1, Earthshine
The Sisters of Mercy - Black Planet
Soundgarden - Black Hole Sun
Tarja Turunen - Lost Northern Star
Thomas Dolby - Moonbase, Weightless
White Zombie - Welcome to Planet Mother******/Psychoholic Slag
Yes - Starship Trooper
ZZ Top - Planet of Women

Any others I might have missed?