I've posted a test version of my "yge" driver (Marvell Yukon Gigabit Ethernet, but it also supports some 100Mbps devices) up on OpenSolaris.org. Get it here -- get the file called yge-test.tar.gz.
There is a webrev posted too, if you want to beat your head against the wall.
If you do test this, be aware that many possible PCI ids are not in the installer file. If you want to test more, please do so (at your own risk). If you find that other devices either do work, or do not, please let me know -- send mail to garrett.damore at sun dot com.
Thanks, and enjoy! (I'm hoping to get this driver integrated into SNV 123.)