Spot on about Wikipedia there, I wish I knew enough to contribute to it more! I pick up little things when I can, and I got involved with the thing a couple years back asking for pics of nature reserves and sites of scientific interest. There are a rare few spots now where the only pics are from me (solely because they're not that significant relative to how hard they are to get to, but hey I had a good day out getting them)

I've been using Street Complete to help with OSM for the most part, it makes it dead simple. I just log on to the actual website to correct more complicated stuff, or occasionally clean up mistakes I or someone else has made