For those who are interested: On 22 September 2013, German space agency DLR and the European Astronaut Center EAC will have their open day again (sorry, German language only – don't know when they will have an English version available).
Present in any case will be German ESA astronaut Alexander Gerst and Italian astronaut Samantha Cristoforetti. Actually, I expect more of the astronauts to be around.
Also happening will be Social Space, something like Space Tweetup. Deadline for registration will be August 26.
With the Social Space thing, I don't have any experience but I have been to the DLR open days in 2004 and 2011. The event takes place over the whole DLR area, which is quite extensive, so lots of walking.
Laboratories open their doors. Planes can be visited, lectures can be attended and astronauts sign autographs. Both events in 2004 and 2011 were very crowded.
At EAC, the ESA astronauts were sitting on a table three each for half an hour, where after another group of three went to sit there. Queues were very long, so sometimes when you stood at the end of the line to get your stuff signed by astronauts A, B and C sitting at the table, it could happen that meanwhile, when it was your turn, astronauts D, E and F or even G, H and I were doing the signing.
Eventually, I tried to catch them when they were just standing there or walking along me... In 2011 I didn't even try to get autographs but visited other interesting things with the folks I was with.
Anyone else have other experiences?