The Steam Family Sharing service is now available to all Steam users, after spend quite a long time in beta testing. With this, users are able to share their entire library with family and friends. Putting those games that have gone unplayed for months and years to good use.
Family Sharing on allows up to 10 other computers to gain access to a single library, but should be more than enough for a single household and several friends. There is a catch though, as the service only allows one person to access the library of games at a time. Which limits how useful this will be. Guests accessing the library will be granted a short amount of time to save and exit the game if the owner logs into his account.
Saves and achievements are stored differently, although borrowers will not be able to access games that require a subscription or is region locked.