I'm a longtime reader of Wikipedia, but have only recently signed up for an account (early 2010).
When I make edits, they are usually fairly minor, made for spelling and grammar changes, and the like, although sometimes I will make changes for blatant, glaring factual errors (incorrect years on timelines, incorrect band listings, etc.).
Most of what I edit will more than likely be in the Technology (mainly computer programming and Apple Computer) area, or in the Mathematics area. Also, you'll see me in the music areas, as well, as I'm a music buff in addition to being a programming geek and Apple Computer nut (I don't consider myself to be a zealot, but I am a big fan of most of what Apple, Inc. has done in the last 10-12 years or so).