While biased in some places, Wikipedia houses content that otherwise wouldn't be so readily available. I donate once a year and will continue to do so.

As I see it, I use the service, so I should throw them a bone now and then. Same as I do for apps - even if I'm not so interested in the extras, I'll toss a few bucks here and there because I think if you get use out of something the creator should reap a reward. Otherwise, we're all just working for nothing.