We are American citizens who plan a 2 week trip to China in November. We will be staying with friends in Shanghai. What visas or other documents do we need?

You need a tourist visa (L visa) to China, you just need to take your valid passport and the valid L visa on your passport to enter China, you don't need to any other doucments.

If you want to apply for China visa in France, you need to prepare the following documents:
1.A valid passport as well as a copy of its information page: Your valid passport must have at least six (6) months of remaining validity and at least one blank visa page in it.
2.Application form: Completed Visa Application Forms V.2011A and V.2011B
3.Photo: one recent photo of 2x2 square inch (black & white or color is acceptable) glued or stapled on the application form.
4. valid French visa or residence permit