Duff-Man says....well, the obvious place to look is ~/library/preferences which should cover the majority of applications. Those pref files are small however and are not using a lot of dosk space (not that it isn't nice to tidy stuff up once in a while too). Other places that files *may* get put are in ~/application support - if an app puts stuff here it will normally create a folder for it. Some apps may put stuff in your system or in the /library/ folder...if it is a well written app/installer it should have an uninstall option when you launch the installer....or you can open the install package using Pacifist and it will show exactly what is being put where.....oh yeah!
