Loger is an Windows Home Server addin which allows you to set timed access limits for each user for the computers on your home network. For example, if you wish to limit the time your son/daughter can spend on the computer to 2 or 3 hours a day, then you can do this through Loger.
Windows Vista and Windows 7 (download) have a similar feature, but of course this has to be set on each client and does not force the user to log off. The add-in is currently in an early beta, and Jose is looking for testers to provide feedback and support to allow him to further develop and complete the add-in.
More info: Loger