Sourceforge hosts the librsvg development mailing list. From our project page, you can subscribe to the list and view the archives.
Visit the #librsvg channel on the GimpNET network at irc.gnome.org. Popular IRC clients include X-Chat and Mozilla.
librsvg is maintained in GNOME CVS. You find information on how to check out the librsvg module on developer.gnome.org.
Developers interesting in helping out should take a look at the TODO file in CVS, as well as the librsvg product in GNOME bugzilla.