Among others PRO BAHN

• is fighting for a fair treatment of public transportation compared to automobiles (e.g., establishment of a nation-wide system of corresponding services including trains and buses, consideration of costs of environmental damages caused by each mode of transportation)
• is informing people on special fares, new lines, better equipment, etc.
• is organizing trips and journeys using public transport
• is negotiating with politicians and decision makers of local transit authorities to improve all modes of public transportation

The most interessing page - though in German - for people from outside Germany certainly is a survey of links, where you can find timetables and information about fares [often with English comments]. It includes most countries in Europe as well as regional information of Germany, the latter often including also information on buses, tramways or subways.

Furthermore, some links containing addresses of companies relevant for public transport can be found.

Sort of a "users' guide to German train" can be found here. As this website is not maintained by us, we cannot guarantee for its content (but it seems to be very helpful).