There are many free applications out there to clean Mac OS X Snow Leopard well inside, but without a doubt one of the simplest of all is Maintenance.
Created by Onyx developers, this application has been conceived for those who do not want complications when cleaning their Mac with weekly or monthly scriptsInstead, they want to check a few boxes and clean it up.
It allows you to empty the system and application caches, redo the Spotlight index or delete all diagnostic reports, to name a few.
Download | Maintenance