Brian has an excellent post about installing OpenSolaris on the MAC. As he notes he is "not the first to document this configuration (1).
However, I wasn't successful with any of the other approaches I
discovered. Maybe this was because it most cases they were using a
pre-release build of OpenSolaris 2008.05. So, for what it's worth, here
are the steps that led me to success... "
Check it out here:
http://weblogs.java.net/blog/bleonard/archive/2008/05/_opensolaris_20.html
I found Brian's blog helpful when installing on an Intel iMac 24 inch. The only diference was that I had to:
sudo fdisk -e /dev/rdisk0
instead of:
sudo fdisk -e /dev/disk0
That missing 'r' stumped me for a while.