Even I have donated!!!

Some people can't donate but most have them have contributed in form of content. Wikipedia can find a way to monetize it. Red Hat is doing it, Ubuntu is doing it, Mozilla is doing it.

Maybe they can publish a book, journal or something. Also, they can show ads to registered people who have no issues with ads. Google Chrome's or Microsoft's banners are not that vivid and we can deal with it. I still visit wired, lifehacker, engadget despite the ads. [Again this could be kept optional]

* Just my two cents :-D