Eclipse is an open-source IDE written mostly in Java. The project originated at IBM and was turned over to the Eclipse Foundation in 2003. It is primarily used for developing Java. A package manager, CVS functionality, a debugger, and an editor are available with plugins (included in a one-time download from the Eclipse website). Plugins have been made for a variety of other programming languages as well, including Ruby and C++.
See the Eclipse Foundation website: http://www.eclipse.org