The people at NASA Goddard Space Flight Center have built a really nice tour of their facilities and all the stuff they do there. Being a space nerd, I find their videos and information fascinating.
Or, in the words of NASA's Karl Hille:
We thought that, being NASA, we shouldn't bore people with a bunch of building walkthroughs or campus maps. Instead it should focus on what we do — which is sending robotic spacecraft all over the solar system to monitor the whole fricking universe.
Karl is absolutely right. Now, go visit their new site and enjoy spending a few hours exploring it. [NASA Goddard Virtual Tour]