There a way to use Steam to back up game saves?
 

what it says on the tin. I know it can be used to save settings and stuff, but what about actual game saves?

I'm pretty sure that, as long as you're playing online, your save gets synched with the steam cloud every time you save. If you play offline and save locally, it asks you which save you want to use.

That's how it works with most valve games, anyway. I'm not sure if that applies to others as well, though...

For games that aren't supported by steamcloud, you need to go to C://Program Files/Steam/steamapps/common and locate your save for each game individually.