Depends on what kind of photography you're into.

For structural/night scene:
If you'll be in Shanghai in the next month, the Expo is a wonderful place to photograph. I especially enjoyed shooting at night with all those lights. If your trip to Shanghai is post-Expo, you can still visit some of the permanent pavilions.

For the skylines:
I know you've photographed this before, but maybe only on land? If you get the chance, take a ferry cruise (usually an hour long and RMB80 a ticket) around Pudong and the Bund around sunset. I guarantee you'll get some spectacular shots of the bridge, passing boats and the skyline.

People-watching, Street photography:
Xintiandi, Huaihai Lu, and Shanxi Lu would be good places for that.

Off the beaten path:
Taikang Lu is a gallery/bar/restaurant area (I call it a hutong maze) which is fun to photograph during the day or night.

Any Bird/Flower/Insect market lends itself to some interesting, often bizarre scenes.

Actually now that I think about it, farmers markets in the early morning hours would be great fun to photograph as well. Full of local flavor and photo-journalistic opps. I need to remember to do that on my next Shanghai trip :]