I checked a few days ago and they weren't accepting Bitcoin. I thought that was a bit weird considering how so many other organizations and companies have started accepting Bitcoin. I checked back to the same section on their FAQ today and it looks like their policy has changed. They seem to be accepting Bitcoin donations now:
Why does the Wikimedia Foundation accept Bitcoin?
The Wikimedia Foundation, as a donor-driven organization, has a fiduciary duty to be responsible and prudent with its money, while striving to provide as many methods of donating as possible. Our donors indicated that they were interested in supporting us through Bitcoin, so after some investigation, we set up a method to accept those donations. See our blog post for more information about it.
Link (scroll down or search for "Bitcoin"):http://wikimediafoundation.org/wiki/FAQ/en
This is good news.