There are a raft of utilities that provide a front end for the built-in Unix system tasks. Some are free, some cost a little bit, either through a purchase or shareware fee. Cocktail is a great example of a paid app that is very complete but it's not free. OnyX is a good free app with similar capabilities.
IceClean does a whole basket of system fix-ups and the price is zippo. We took a look at IceClean a couple of years ago, and it's been updated for Snow Leopard. Everything from triggering background maintenance tasks that normally get
