There is no paperwork required to obtain prepaid sims in Shanghai (or Beijing for that matter), though some cities (Tianjin comes to mind) require a passport scan. Buying a SIM on the street is easy as pie. My post upthread about spending 40 mins at China Mobile was in regards to post-paid cards.

As I mentioned in that post, IMO postpaid cards are absolutely worth the wait for people that spend more than 30 days per year in China. You don't need a residence permit or a Z visa to qualify; a passport and a local bank account will get the job done.

For those of you that absolutely have to know your phone number before you touch down (e.g. maybe you want to print business cards), my advice is to ask your hosts to pick up a card for you and email you the number. If that isn't an option, aside from sites like the one pseudocrow mentioned, eBay is an excellent place to shop.

Switching topics here, I'm personally not a fan of Haiku/Hatsune, it spite of its popularity. I like Japanese food quite a bit and there are a number of less famous restaurants in both Shanghai and Beijing that deliver a much better (and fresher) product, albiet without the snazzy interior design and romance factor. In Shanghai, I like the place in the Ruijin office tower and Suntory (at the top of the HSBC building). In Beijing, Yotosuba(sp?) reigns supreme.