Steam has announced the availability of a new beta client for Windows and Mac that will allow users to remotely manage their accounts from their phone or the web. This includes the ability for remote downloads of games, meaning you can start downloading games to your home computer while you're slaving away at work and dreaming of the Orange Box.
The new beta client was announced via the Steam forums. It also offers reduced excessive system memory usage while downloading updates and added debug code to diagnose download issues. Judging from the forums, some people aren't seeing remote management immediately when they install the new beta. There also seems to be a few reoccurring bugs (Steam has already issued fixes for two).
To check it out for yourself, go to File -> Settings. On the Account tab press the Change... button to open the Beta Participation dialog. Then Select "Steam Beta Update", and allow Steam to restart itself.