Apple - What file systems can Snow Leopard read?
It might be easier to connect the machines on a network and use rsync, nfs or ftp to copy data, no extra software would be needed.
If you want to do this you will need MacFuse which allows OS X to read other file systems. A tutorial for ext3 is on this blog.
If you are planning on doing this a lot, there are commecial packages too:
http://www.paragon-software.com/home/extfs-mac/
There is a free alternatives also though through MacFuse/FUSE:
http://sourceforge.net/projects/fuse-ext2/files/