I have been a user of Wikipedia since the days when the number of articles where less than 100,000. However, I've only recently created a user account. I would be happy to brag that I've created, edited and corrected a number of pages, but I've always done so anonymously.
My interest lies in Computing (programming and free software), video games, biology, physics, music (baroque mostly), and I could probably carry on. I'm a 'Random article' whore, and there's little that doesn't interest me.
Most of the edits I've done were to clean up spelling and grammar, convert imperial measurements into metric, change American dates to international date format, etc.