I went to the Giant Panda Breeding Center from the city by taxi and it was well worth it. Go as early as you can. The pandas get to go outside early and munch on bamboo for a couple hours. By 10:30AM most of them seemed to be asleep - besides a few younger ones.
It was a bit crowded towards the end.
I did not have the time to go to the Dujiangyan panda base suggested by jiejie but unless you are really into panda bears option 1) should be OK.
Note that the souvenir plush pandas inside the center are expensive and not of good quality. Outside they are cheaper ($2 for a medium size one) but quality is still bad.
The Intercontinental Century City has a very nice one as Ambassador welcome gift, though.

There is a nice old hutong style covered food market just east of the Crowne Plaza City Center that is well worth checking out.