Actually, for some games, Steam will do that too! I don't know when the released it, but if you look in your Steam Library, if the game has a little cloud icon next to it, your saved games and other settings will be shared between computers. Right now on my screen, COD2, Torchlight, Dawn of War II, and a few others all do this.

If you go to the Steam menu -> Settings -> Downloads+Cloud, then check the box for enabling steam sync for games that support it.

You mean something like this? http://www.steampowered.com/steamworks/ov_cloud.php

It was introduced to Left 4 Dead late 2008. I'm not sure how widely it's used at this point.

In settings you can enable it at the bottom of the Downloads + Cloud tab.

Here's a list of which games currently support the Steam Cloud. http://www.giantbomb.com/steam-cloud/92-4581/games/

or you could save your games in a dropbox folder - works great for the couple of steam games I own