Shanghai- what a brilliant city. Everything they say is true. Money and sex hang from the lamp-posts there (although not like Bangkok, as this is undeniably a police-state).
Walking through Shanghai is part Tintin comic book, part 1930s gangster movie,with bits of Stalinist workers' paradise and Jetsonesque Futurism thrown in. Best of all, Pudong, the city built to be viewed on a pedestal, looks on with mild amusement (best viewed from the Bund, one of the best streetscapes in the world.
Here is my brief tour-

1. First take a walk on the Shanghai Bund
Beware of the confidence tricksters. It's easy here to imagine yourself in a glamorous 1930s Shanghai, a place of wealthy Jews, Japanese, Germans and Russian prostitutes. A final party before the reality of Modernity caught up (Japanese invasion).
2. After this, turn left at the Peace Hotel and walk up the Nanking Road shopping district.
This road, referred in the past as the “No I street in China”, was the main shopping street of old Shanghai. It's still alive with all sorts of freaks and criminals, and is an okay place for a wander. Interestingly, all the old department stores and hotels are all still there sitting in decrepit splendour.
3. If you survive this (its actually very safe, just don't accept any invitations to tea) you'll end up at the old racecourse (Peoples Square Area).
When I got out of the subway when I first arrived in Shanghai I thought I'd ended up at the Bund. This was the other end of old Shanghai, the pleasure and vice end balancing out the Bund. The Communists, never ones to miss an opportunity for a bit of fun, turned the racecourse into a combined rally and execution ground (Sydney could use one of those...). Anyway, it is a curious socialist park now, but ghosts of the opulent past remain.
4. While in the area, have a look at the adjacent Post-Modern wonderland of Puxi. The modern shopping areas are here.
5. Finally, the piece de resistance, Pudong.
I'm not sure if this should only be seen from afar or if you venture into the area (it is a bit dull after Shanghai, but the McDonald's and Apple Store are welcome repites. You can get there using a really groovy psychadelic train (incredible light show) under the river.
See also- Top Ten Shanghai    the architecture you must see