We have IGMPv3 in the kernel now. All that's holding us up is a few header files in glibc:
http://sources.redhat.com/bugzilla/show_bug.cgi?id=5
I'm not sure who looks at the source.redhat.com bugzilla. Perhaps I should file this in the FC bugzilla?
It would be nice to get this in FC3-devel, and FC2 errata too.