I strongly recommend to visit Retrogamers in Karlsuhe. You can go there on tuesdays and saturdays. Tuesday is more a meeting of the members but also open to public. Saturday is a bit more busy due to the disco in the same building (even on the same floor). If you're into dancing to modern music (utz utz utz

) you can combine that. If you're more into talking to the people there I recommend to visit them on Tuesday.
For Amusement Only is also a great place. As Settler said, there's only one saturday in month (the first IIRC) for the public but I'm sure there will be a chance to go there if you ask them...let me know, I'll forward you

Unfortunately they are forced to leave their building 'til end of June. At the moment they are looking for a new location.
And finally, if you're around this area you are invited to visit Dirk's (Capt.Kirk) and my collection in 67435 Neustadt

Luigi