Lazarus, a cross-platform IDE for Free Pascal, a 32bit / 64bit professional ObjectPascal compiler.
Emacs - Powerful IDE, extensible in LISP, ships with modes to integrates with SCM (GIT, SVN, CVS...), build systems, debugger and even fancy multi-window with ECB.
VIm - Powerful IDE, extensible with scripting, can use various modules for completion and more.
KScope - Cscope based source editing environment with KDE.
QtCreator is an nice IDE which has code completion, remote deployment (with version 2.3) and Outline view. It also has an VIm mode. Its menus are much cleaner than these from Eclipse and its easier to get started with this ide than Eclipse for that very reason.