Just in case anyone is bored... :)
http://sandeen.fedorapeople.org/ext4/fsck-segfault-images/
contains about 6 intentionally-corrupted ext4dev images which each cause
the e2fsck in the next branch to segfault for me on x86_64.
I'll find some time to look closer, but just thought I'd put them out
there for now.
-Eric