Useful Eclipse Plugin

Subclipse
Subsclipse is the Eclipse plugin for subversion (SVN). With this plugin you can tightly integrate your project with the SVN repository.

JadClipse
JadClipse is the plugin for JAD (Fast Java Decompiler). It can be use to replace your original class file viewer. So that you can view the source of any class file (include class file in the JAR file) in your project by just double click.

FindBugs plugin & CheckStyle plugin
Both FindBugs and CheckStyle offer eclipse plugin. You can find plugin of FindBugs in its download page page. Checkclipse is the plugin for CheckStyle and can get it from here.