As usual, not that immediate to find a proper answer on the ‘Net, hence I’m providing one here.
While in Snow Leopard was quite easy to see your ext2/ext3 formatted disks via MacFuse and ext2-fuse, in Lion you need to install another fuse fork and select a special option. That new fork is OSXFUSE, which latest release at the time of this post if from December 2011.
The most common symptom indicating you need this is to try mounting an ext2/3 formatted drive and see the following error:
fuse-ext2 /dev/disk3s1 /Volumes/Movies dyld: Library not loaded: /usr/local/lib/libfuse.2.dylib Referenced from: /usr/local/bin/fuse-ext2 Reason: image not found
During the installation of OSXFUSE, you need to enable MacFuse Compatibility Layer by flagging the appropriate checkbox as shown below:
Once you’re done with this, replug your ext2/3 formatted drive and it’ll automagically mount it in Finder, giving your deserved magnificent user experience of a Mac user 😉