Xfig
Xfig is a Linux program to draw diagrams.
I recently used it to draw EER (extended entity relationship) diagrams. I didn't find a library for these EER diagrams so I created one. If you're interested in it you can download my EER library and use it for free.
Although I hope it's useful there is no guarantee it works for you, it is correct or it will suit your needs.
You're here: Xfig.
Last update: September 20, 2004
(c) 2001-2008 Florian Fankhauser, http://www.flof.at/