I love taking photographs, but I'm too much of a nerd about it: I also like window-shopping the cool camera systems that I can't quite rationalize purchasing, and if I go on a trip I'll pack two or even three cameras along. It's so pathetic!
While I like looking at cameras, Shanghai is not the best place to buy a camera - I think that title would go to the US or Hong Kong. It's too expensive, and some things are just not at all available. However, there are definitely fun places to look around, and there's unique products that can't easily be found elsewhere.
I'd like to go from easiest to hardest, but I'll get this out of the way first: taobao.com should be a buyer's reference. It's a Chinese EBay, with a few slight differences - it's almost entirely e-shops with set prices, and the money is held in escrow until the buyer is satisfied. It also requires a Chinese bank account that has been set up for e-purchases, and the site's language is all in Chinese. However, generally it offers the best possible price for items, and shows what's available in China, so it's a useful starting point. Also, entering the English names of equipment into the search box usually is fine, and will give about as many results as using Chinese. I've used taobao a couple times with no problems.
So with that out of the way, I'll say the places for getting cameras:
1) Xujiahui - Best Buy opened a branch in Xujiahui district, it's part of a larger plan of expansion into the Chinese market. The environment is about the same and I generally think it's dependable, although the return policy is less generous than in the US. Many of the workers there speak English, and the selection is pretty good, if entirely digital and not excellent - they only have Nikon and Sony DSLRs - they'll sometimes stock Canon but they don't carry Canon's lenses or equipment. It's easy to hold onto and test out the equipment. The prices are generally up to 25% more than it would cost in US, however, and that was true even before the dollar's recent travails. A year ago I managed to get a camera there for much cheaper than the US price, so maybe there's some luck involved. Even if it's cheaper elsewhere, I'd be tempted just to go there as it's the least hassle.
There's also a lot of shops selling digital cameras in the electronic malls immediately nearby, really it's a bazaar of little stalls. The prices as listed are very very high. I haven't tried bargaining with them, I'm sure you'd have to bargain pretty hard and a foreigner wouldn't get a break. I doubt it's worth it.
2) Huan Long Zhao Cun Shi Chang - a photo mall directly across from the North Train Station, at 360 MeiYuan Street. It had been closed for re-building until recently, and is still in the process of being set up, so there's obviously many more stores to open. Hopefully that re-building process will involve a sign - right now there's only a non-distinct, Chinese sign. It's on the 2nd and 3rd story of the mall across the street from Subway Line #1's Exit #4, and there's a Burger King around the corner, to the left of the entrance. The 1st floor is a normal department store.
While I've only bought a single roll of film there, it's a bunch of clean, brightly lit stores, with long hallways where it's easy to get lost. It centers around digital cameras, with some shops selling used but excellent-condition cameras, at a premium cost. I saw the Nikon D3 there, which is supposedly really hard to find even in the US. Prices seemed to start high but I'm sure there's room to bargain. There's a few places selling film, and a few places selling books about photography, and other stores selling general photographic equipment.
Some of the places will speak English, some won't. Most (all?) places will charge slightly more if you want the receipt than if you don't. It's so they can avoid taxes.
3) Xing Guan Photographic Mall - I really like this camera mall, although the feel is only a step or two above a large flea market. It's six floors, on the corner of Luban and Xietu Lu - not very far from Luban Lu Station, on line 4. The first floor is digital, the upper floors are used equipment, flash equipment, camera repair places, and other general equipment that would be useful to a professional photographer.
I especially like the used equipment shops, mostly on the fourth and sixth floor. A lot of it is very old school, cameras that look like they saw better days in the 50s. To my surprise, there's not as many Chinese cameras as I expected, and very little Russian. Much of the vintage equipment is German. It's more expensive than EBay, but not terrible. I get the idea there's little room for bargaining at most of these stores, which I'm fine with.
For me, I'm somewhat interested in getting an old Medium-Format Chinese camera. Both the Seagull TLR and the Hongmei HM-1 folding-bellows camera are to be found, for around $30 before bargaining. There were pretty good prices on Mamiya systems and the like, which is probably a better idea.
Similarly to Huan Long, some of the places speak English, some don't, and they give you a small break if you help them cheat with their taxes.
It's definitely the best place to get film - there's a number of stores with a good selection, and the prices for non-professional film are good. One little oddity is, it's impossible to get 1600 film in Shanghai, and I've only once seen 800 film! 800 is available at every drugstore in the US, but even on taobao.com is only available as a Hong Kong import - I find it very mysterious and annoying. In the meanwhile I've become a big fan of Fuji Superia ISO 100 film. I think the crazy red and yellow saturated colors work very well in China, where people often like to have bright red and yellow decorations. It's available as 120-size film, I believe that's not true in the US. It goes for $1.50/roll.
There's also local brands of film, which really aren't very popular, the most common being Lucky, which is easiest to find in ISO 100 B&W. There's other brands like Shanghai B&W or color films, I haven't tried them but I hear they're not as good as Lucky. Lucky film is kind of eerie looking and I hear quality is inconsistent and really it's ISO 50 (which doesn't help on overcast Shanghai days), but a roll of 120 film goes for $.75, so...
4) Wei Ma Professional Photo / Frontier - two film photo stores which are right at the entrance to neighboring alleys, with Wei Ma focusing on Kodak, and Frontier on Fuji. On 457 & 459 Wulumuqi Lu, South of Yan'an Lu, on the East side of the street.
Shooting film is cheap in Shanghai. Getting a roll of Fuji developed at Frontier only costs 5 kuai, about seventy cents. It's twice as much in Wei Ma labs, though. They both charge a lot more to develop B&W. Development at Frontier usually is ready several hours later or the next day, Wei Ma takes a couple days. I normally use Frontier. Wei Ma does have English speakers, though, and it makes medium-format prints for 2.5 kuai/picture, not 5, it also stocks chemicals for B&W developing. They also have a stockpile of expired Feb. 2006 ISO 100 Kodak Portra 120 film, marked at 15 kuai/role. It's been stored OK so I'm guessing it should be fine.
35mm prints are a little expensive at 1 kuai/print, but I just scan the film up at home. They'll scan a roll for $5, I tried it at Frontier once but wasn't happy with the results.
There's also a million Kodak stores & stalls all around Shanghai, they're fine for making prints off a digital memory card, developing a roll of film, and small things like that.
Update 4/15/2008 - I also have a word to say about Buying Holgas and Toy Cameras in Shanghai.