I have recently needed to mount an ext3 formatted partition on my MacBook Pro laptop. Silly me thought all I would need to do is plug it in and at most mount it with the command line. Not so…
First you need to install the new fork of the ext2-fuse module called OSXFUSE. Download and run the install. Make sure you tick the box to install the MacFUSE compatibility layer otherwise you will have problems later.
Next install Fuse-ext2, once done if you plug in a ext2/3 drive it should just mount automatically. Currently it is read only. I restarted my computer after installation but this might not be required. I was due a restart anyway.
Why they can’t include native support for a few more formats I don’t know. Seems very silly not too.