If you wondering how to uninstall plugin in Eclipse Helios (the current newest Eclipse version) you can bury your head in sand :) . If not, follow these steps:
Help > About Eclipse (at the bottom of menu) > Installation Details > Installed Software Tab > Select the plug-in which you want to uninstall > Click “Uninstall” button
P.S. By the way, when you open “Installation Details” window there are some tabs: Installed Software, Configuration, Installation History and etc. It is useful information if you need information about Eclipse configuration details. It won’t be necessary to open configuration files from Eclipse installation folder.