I'm not sure exactly what you mean by 'lightweight,' but here are a few popular IDEs for linux:
Anjuta for Gtk/Gnome
KDevelop or Quanta for KDE
CodeBlocks runs on Windows/Mac/Linux and is written in C++
None one of these are Java, so they automatically have an edge over Eclipse for performance ;)
Another option is MonoDevelop, which is geared towards .Net/Gtk# programming but also includes C++ support.
