Scratch

Here's a list of cool games (not on scratch) for you to try out when you're bored. Please contribute by filling out the details to your favorite (or not so) games.
Name of game:
Online or download (or both):
If download, which OSs? (mac or windows or both)
What you do:
Is full version free?

Please only put free games here, or at least games with a free part to it (like mc)

List:

Blockland-Download, Mac and Windows, You build stuff. Free demo doesn't have multiplayer.
Minecraft-Browser (free and paid) and download (paid), Windows, you craft stuff and find mines... Free version is old, no crafting, just blocks.

Add more!