There were actually several different lego space shuttle models of various sizes and complexities, many of which are now out of print. You can find most of them on ebay now, but expect to pay a bit for them.
One had a
full launching tower and SRBs+fuel tank. The best one was a
Technic set with working cargo doors, robotic arm, landing gear and the ability to have some of the movements electrically powered, and fiber-optically lit.
Heck, the whole group of
"Discovery" sets are pretty cool. I know I saw a website showing a combined Mindstorms kit and the
MER set to make a mobile lego MER, but I can't find it now.
The lego James Web Space Telescope was shown at the 2008 American Astronomical Society meeting, in the NASA booth. I'm pretty sure it was the same model as the one linked above. There were a lot of astronomers ogling it...
I'm waiting until I get a real job and a house where I can put a proper "lego room". Then its time for a shopping spree!