http://www.microsoft.com/opensource

That's cool URL. http://www.microsoft.com/opensource I mean. The announcement at port25 site goes like this:

Today, Microsoft took another step in its relationship with the open source software community. We did this by bringing up a new web property that clearly outlines Microsoft’s position on OSS by providing specific information about Microsoft, the OSS community and the interaction between the two. The new site also details information about getting started with OSS and Microsoft technologies.  We'll keep the site updated with new content featuring Microsoft’s engagements with the OSS community - be that events like OSCON, partnerships, offers or just interesting articles highlighting different work we're doing across the company. Port 25 will continue to be the source for technical analysis and community with the Open Source Software Lab.

And of course it has a link to the John Lam's IronRuby announcement right on the front page.

There is even "Open Source at Microsoft" feed, consisting mostly of case studies, for those interested.