Microsoft bought Lookout, the small company that makes excellent Outlook search tool. Lookout uses a variation of the highly-regarded Lucene search engine to power its amazingly fast search.
After the acquisition, the app was upgraded so that the software agreement is with Microsoft instead of Lookout Software. So we now have the first bit of Microsoft software licensed under an Apache license. A milestone, of sorts.
Update: That bastard Michael pointed out that Joel had already noted this. Joel had assumed Microsoft wouldn't redistribute the app with this license, but it seems, given that they just sent out a version 1.2 update to all current users, that they've done so anyway.
FYI -- MS have been shipping GPL'd code since January of last year at least:
http://sourcefrog.net/weblog/2004/01/08#plapack