Deleting unused programs to make some space for Lion? You need an app like recently updated TrashMe. It's an app uninstaller with both drag-and-drop to uninstall and application listings that will handle any program you have installed, widgets, Preference panes and even plugins, moving them to the trash with their associated files.
TrashMe will also scan user configurable folders for applications, places like the Downloads folder, from which you might have fired up a program once, but never really used it and forgot about it. You can set certain apps as protected, with the Apple default apps protected as standard, just so you don't accidentally delete something important.
Like AppCleaner and AppTrap, TrashMe also supports intelligent Trash monitoring (Smart Detection), allowing you to just delete an application the way Apple intended. It will then detect the trashing of an application and offer to find any files that might be associated with it.
With the help of a little add-on that can be downloaded from the developers site, TrashMe can also delete files and applications that you don't have write access for. There are also some "hidden" OS X preferences TrashMe can change too, which include the suppression of .DS_Store files on network volumes, a setting to show or hide hidden files and folders and also the ability to disable the warning that OS X pops up when you launch downloaded applications for the first time.
TrashMe version 2 is a highly polished uninstaller app that is currently available for US$4.99 from the Mac App Store.
Thanks to topherrjames for the suggestion.