Yes, as the title says, .NET will be running on Mac OS systems in the future.
I was searching a different requirement related to my work for Mac OS and foundout this interesting post where Scott Guthrie (Senior Microsoft Official, and incharge of various .NET technologies), and other Microsoft Officials reveal about the future plans.
Here is the URL for you to findout more
http://weblogs.asp.net/pwilson/archive/2007/01/13/breaking-news-future-version-of-net-framework-to-run-on-the-mac.aspx
Regards - raheel