the nurburgring (old road corse) is available for open lap sessions. It's VERY dangerous! no run off and lots of armco. People ride it on a bike, but it's more like a good favorite back road than a race track. Not that it sucks, just can't run it at race pace. A BMW/Porsche might be a bit more fun.
There's actually a taxi service that'll take you around the course at race pace. It's a BMW M5, driven by a pro driver. Price is something like $500 a lap (!!!!)
The race track at nurburgring (where WSBK ran) is a whole different deal. Very much a real track, but a club/magazine would need to rent out the facility. Germany is very expensive for that kind of stuff, so save your Euros.
Locals tell me the Eastern Europe is all the rage for track days. Bruno, Poland and a few other places are gaining popularity mainly because of cost and small crowds. Euros go a lot further there.
I remember seeing a few clubs that sun Spa Francop (sp??) in Belgium. Assen was very tough to find any clubs that run there. Most of the local track day org websites where in German or Dutch. I think the rationale is that if you speak English, you're coming form England, and are 10 times more likely to go to Spain. Which by the way, is the ultimate place for track time ;-) Zero rain, perfect temperature and pretty low costs vs. Northern Europe. I know a few clubs that run Valencia, Jerez, Catalynia, and a half dozen or so private tracks that magazines use. Germany/Holland gets a lot of rain, so if you're going to travel, head south! Food is better as well.
I did one day in Catalynia. Tons of fun, but very different than in the US. Hardly anyone had a dedicated track bike and no enclosed trailers. Lots of people had their whole family there, like it was a real race or something. The safety at those tracks are unbelievable. I don't think I could hit a wall if I tried.