Not sure if this belongs here, but thought it worth mentioning. There is an English-language "Rhine Magazine" which has been going for a couple of years now. It's published bi-monthly for 3 Euros a pop and has pretty comprehensive listings and general info for Duesseldorf, Cologne and Bonn, plus articles on issues of local interest (eg: Feature on Yoga & where to find classes in this months' issue). I've found it useful for the occasional 'what-to-do-with-the-kids-on-a-rainy-Sunday-afternoon' tip. Further info:
Rhine Magazine.