Mac OS X is a wonderful piece of operating system, where everything is just a matter of «drag and drop». Even though you could simply put an application in the trash to delete it, you would be missing some related files created by this application (preferences, temporary files...). You need to know that these files can waist several mega-bytes on your computer.
TrashMe will help you in the uninstall procedure: drop an application on TrashMe and it will find related files for you, so as to delete everything. Thanks to this advanced features, you'll be sure that those applications will be completely uninstalled.