The netplay setup is pretty similar to Heboris Mini's, but seems to work a lot smoother.
You can get NullpoMino at the Google Code project page
Head to the netplay server's homepage
for current room and player lists and for detailed statistics about the most active players. It's also got release announcements and other miscellaneous Nullpo-related news items. And be sure to thank xlro for running the server and for everything else he does!
If you're having trouble getting things set up on your own, jennr246 has written a guide here