I just made my first contribution to Wikipedia, fixing up some notation and wording in the article on Schmidt Decomposition. There may still be some bugs to fix up there, but I corrected what I could based on what I know.
I’m always a bit reluctant to reference Wikipedia in public, though admittedly, I spend quite a lot of time perusing their articles. In particular, I’ve spent a fair bit of time looking for definitions of mathematical concepts that don’t appear in any of the math texts that I have access to. There have been a few articles that are not very good, but for the most part, I think the math articles are fairly well written. While I may have some quibbles about wording, the information in the articles on subjects that I do know a lot about is almost always correct.
On a more general note, Colby Cosh tells us why perhaps we shouldn’t be so hard on the online encyclopedia.
Idiot String Theories 