Free SimCity? Free Civilization?

The best SimCity knock-off is LinCity-NG. It has a tendency to crash in Linux, but it runs fairly smooth in WinXP. It's free and open source. The project is abandoned, though.

I'm not sure if C-evo is open source, but it's the best freeware alternative to Civilization for Windows. It's free, it looks great, and it has a map editor! It even has an extremely low filesize of 2.4mb! What more do you need?

I'm keeping a look out for better sandbox games. There's a decent Portal clone in development, but it doesn't seem to be worth posting about yet. I'll keep you in the loop.