I would like to mount an ext2/3 filesystem on a mac running 10.5.
is recent, and links to http://ekettoz.blogspot.com/2009/06/mounting-linux-ext2ext3-partitions.html
which references http://sourceforge.net/projects/fuse-ext2/
This project has releases from December 2008 to June 2009. I know I have some MacFUSE driver for Ext2 at home, but I am at work right now. I can check which one I have back there. It works well, whatever it is.
http://sourceforge.net/projects/ext2fsx/ appears to do the trick.
I should have asked Google before asking ServerFault. In any case, I'll leave the answer here for others.