Sega (a third party developer) is releasing in Japan on May 24 a pachinko game for the Wii that is both online and uses Mii's - two things that were rumored to be unavailable to 3rd party developers until next year. Obviously the rumor was wrong.
http://www.n-sider.com/newsview.php?type=story&storyid=2666
And here's the page for the game in case you read Japanese, but there are screenshots showing Mii's:
http://sega.jp/wii/pphokuto/
Also, this interview with Activision indicates they are also working on online Wii games:
http://au.ds.ign.com/articles/770/770831p1.html
http://www.n-sider.com/newsview.php?type=story&storyid=2666
And here's the page for the game in case you read Japanese, but there are screenshots showing Mii's:
http://sega.jp/wii/pphokuto/
Also, this interview with Activision indicates they are also working on online Wii games:
http://au.ds.ign.com/articles/770/770831p1.html