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]