I am plnning to visit Chengdu from 23-30 Sept '12 for the Fair, Pls suggsest best place to visit

Since you have about 7 days in Chengdu, I think you can not only visit Chengdu, but also some other places around.
In my opinion, Jiuzhaigou and Huanglong are the best places that you need to go, which will take you about three days. Two days in Jiuzhaigou and one day in Huanglong. There you can enjoy the beautiful natural scenery. I think it is a paradise.
On the other four days, you can travel in Chengdu. Chengdu Panda Breeding and Research Center is a must seeing place. You can see many cute pandas there.
The Three-Star Piles Musuem is also worth seeing, where you can enjoy the Shu culture in Chengdu.
Jinli Street is a place to get close to the local people and find some local snacks and beautiful artwork.
This is my advice and I hope you can have a wonderful trip in Chengdu.