Frequent contributor and administrator on the English Wikipedia. I've written somewhere over 550 articles on en:, mostly in "classical" music-related areas, and as of September 2008, have over 80,000 edits there. I have a doctorate in music, but make my living elsewhere. Sometimes I write articles about that "elsewhere"; some of the images associated with them may be appropriate for Commons.
I'm an occasional photographer, and also I make images of musical examples for articles about music: much of that stuff would be better here than just in the local English wiki. I also will be uploading maps -- mainly of places in the United States -- which I make in ArcGIS from public domain or self-created data.