Zen Bound 2 http://store.steampowered.com/app/61600/
Osmos http://store.steampowered.com/app/29180/
Chime http://store.steampowered.com/app/62100
The Tiny Bang Story http://store.steampowered.com/app/96000/
^ I haven't played those 4 yet but they all look very relaxing to me (I think I will try at least the first two some day)
Faerie Solitaire http://store.steampowered.com/app/38600/
^ Seems to be a good Solitaire game
Audiosurf http://store.steampowered.com/app/12900/
Great game; relaxation level depends on the songs you play it with; I recommend slow songs (obviously) and classical music or orchestral soundtracks.
Civilization 5 http://store.steampowered.com/app/8930/
A very complex game at heart, but like all Civ games it's also extremely relaxing imo; on easier settings the AI opponents are not aggressive at all - even though some of them pretend - and you can just sit there, explore the world at your own pace, make new inventions and watch your civilization grow and flourish.
