Share your computer?
Now share your games too.
Steam Family Sharing allows close friends and family members to play one another's games while earning their own Steam achievements and saving their own game progress to the Steam cloud. It's all enabled by authorizing a shared computer.
Currently in beta but access is limited. But you can 'express your interest' by joining this group. This will be fantastic when it rolls out fully.
http://store.steampowered.com/sharing