Shanghai

Da Qing Hua 大清华饺子 (Manchurian) XieTu Lu & DaPu Lu - one of my favorite restaurants in all of China (first discovered it in Xi'an). So good and cheap!

Shanghai
I am terrible for restaurant suggestions... just a few ideas

* Guyi (Hunan)   http://www.smartshanghai.com/venue/1315/Guyi_Hunan_Restaurant_shanghai
* Dishuidong (Hunan)   http://www.smartshanghai.com/venue/2848/Di_Shui_Dong_shanghai
* Crystal Jade (Cantonese) http://www.smartshanghai.com/venue/1008/Crystal_Jade_Restaurant_-_Xin_Tian_Di_shanghai
* Lost Heaven (Yunan)   http://www.smartshanghai.com/venue/2603/Lost_Heaven_-_Yunnan_Folk_Cuisine_shanghai
* Dongbeiren (Dongbei)  http://www.smartshanghai.com/venue/264/Dongbei_Ren_shanghai

Hope that helps...

Beijing
Da Dong (Beijing Duck)
Hatsune (Sushi)

Chengdu
Grandma's Kitchen (or is it Mama's Kitchen) (Homestyle Sichuan Food)
Go to a Tea House
Hot pot