There has been a lot said on these games already. I'm pretty sure I won't be able to add anything new, so I won't bother including my review. There's a short description, so at least you know what you're getting into. Most of these have great audio, so turn up your speakers. Have fun!
You Have to Burn the Rope (Flash - Kongregate)
I think you can figure out what to do. Stay for the song at the end.
A puzzle game fusion of light and sound. The game is still in development, so there are only 15 levels available. Bend the flow of particles and try to fill the audio bars. The music builds as you succeed.
Aether (Flash - Armor Games)
Explore the solar system. Use the sticky tounge of the beast to swing from clouds and asteroids. Fling yourself to other planets. See great things. Bring colour back to the people you meet.
I Wish I were the Moon (Flash - Kongregate)
Take pictures to re-arrange the members of this strange love triangle. Try to find all the endings (7 plus a secret one).
Night of the Cephalopods (Windows)
A simple survival horror game with a Lovecraftian narration that works to set the tone of the game as you play.