Amnesia is a handy app used for scanning and cleaning Mac from junk files. A quick scan with the tool will let you know that you have a great deal of files that were not uninstalled when you thrashed the programs. In order to get rid of the junk files, the uninstaller comes with two separate modes. First one is the simple drag-and-drop action that Mac users are used to; by dropping an application into the main window, the uninstaller will show all the files related to the application. I find the automatic mode to be faster and more efficient, since opening the Applications tab will scan the Mac for all of the applications installed. After doing so, the uninstaller will use advanced tools in order to delete the selected items.
This feature-rich application comes with support for uninstalling and deleting broken or old widgets, screen savers and plugins too, so it has a high applicability. What makes this different from other similar products is that Amnesia is really effective into showing and deleting junk files, since the simple drag to thrash action is not enough to completely uninstall an application.
All taken into consideration, you should give Amnesia a try; it comes with a well-polished interface, it provides tools for uninstalling widgets and plugins and has very good functionality.