I just donated to Wikipedia because I use it everyday. I work as a software developer at the Library of Congress. I'm not ashamed to admit that I've spent the last 10 years filling in gaps in my computer science, math and philosophy knowledge. Working in libraries makes this sort of self-education process easier because of all the access to books, journals and whatnot. But Wikipedia has made this process much more fun and collaborative. I don't think I could do my job without it.
I also am a Linked Data enthusiast, and appreciate the essential role that Wikipedia plays in data sets like dbpedia, yago and freebase in bootstrapping Linked Data around the world. Seeing Wikipedia pages float to the top of Google search results really brought home to me how important it is that we can use URLs as names for things in the world, and gather a shared understanding of what they are.
If you use Wikipedia I encourage you to take a moment to say thank you as well.