MacSSController helps you make your Mac to start/shut down/sleep on schedule. It can, for example, start/wake up your computer at midnight so that you can run backup tools while you are sleeping, or it can start in the morning before you wake up, and download new Podcast episodes.
MacSSController would be much more convenient and useful when used in conjunction with SUL.
Maybe you already know that you can set a schedule by using the "Energy Saver" pane of "System Preferences", but this allows you to set only one schedule. MacSSController lets you set as many schedules as you want.