As you know, if you use a Mac, you can uninstall programs just by moving them to the trash. That uninstalls the program but leaves on your hdd some preferences files which have to be deleted manually (they are too small though, so you do not have to delete them as they do not slow down your mac). AppCleaner is a small, free app that manages to completely delete applications. Another key feature of AppCleaner is that it deletes widgets from your Dashboard with a single click. That is for me very useful, because I do not have to navigate to user>library>widgets to delete them. The video above shows how easy this process becomes using AppCleaner.