You simply don't see soda cans or bottles on the streets of Brooklyn. Similarly, it's sometimes hard to find scrap metal on the streets (I'm the kind of guy who looks for that stuff). You do, however, see plenty of paper products, such as food-wrappers, and tons of plastic bags.
What is the distinction?
Anything that can be redeemed for money--even small deposits of $0.05/ea--is actively scavenged and turned into cash. This is a beautiful consequence of urban society. There are so many people here, and the bell curve of income extends so far to either extreme, that material scavenging is (relatively) proffitable to some. There are homeless people who canvas all the streets of Brooklyn looking for any material that have a deposit. A single can is worth shit, but if you fill a shopping cart with them, you can get a good meal or whatever. In effect, we pay the homeless to clean up certain types of trash, and they do it.
As metal prices have risen over the last few years, this is true for scrap metal too. Copper, brass, and aluminum have gone through the roof. If someone leaves some left over copper plumbing pipe on the street, it will be collected and redeemed at a scrap yard. Again, the homeless are in effect paid to clean up the streets.
Even failing that, New York offers free curbside pickup and recycling of glass, plastics, metals and papers. The variety of recyclable is much broader than I have seen elsewhere. For example, you can leave more than metal cans on the curb, but anything which is "mostly metal," such as old bike frames, refrigerators, air conditioners, toasters, etc.
I often think about systems in which the remaining trash--the paper and bags on the streets--is similarly collected and recycled or reclaimed. There are a few difficulties with that, but I believe they can be overcome.
Paper-as-food-packaging is often not recycled because it has food scraps on it--an overzealous blot of mustard, meat juices, whatever--and unlike metal or plastic food containers, paper products cannot be washed before recycling. If the city tried to offer recycling of this kind of paper, recycling bins would attract animals, and recycling plants would need to perform additional steps to purify the fiber. As much as I demonize these discarded food wrappers, I am old enough to remember when McDonalds used to put each hamburger in a styrofoam container, and I recognize they are the lesser of evils.
Perhaps the only way to reuse this grade of paper would be to compost it, and then use it in municiple parks, donate it to community gardens, and sell it to homeowners or landscaping companies. There is precedent to suggest this could work. Many municipalities dredge their waste treatment facilities, and sell this as compost. Also, I know that some beer breweries sell their waste as compost.
Plastic bags are also tricky. Native New Yorkers may not realize this, but people really go crazy with the bags here. In my native Virginia, people would always ask if you wanted a bag if it were clear that you could get along without one. When I moved here, I was surprised to learn that they always try to give you a bag. I had never thought of putting cups of coffee into a bag until I moved here. I've bought single, self-contained products, like a gallon of milk, and sure enough they'll put it in a bag if you're not quick enough to exclaim "but it's already got a handle!"
Plastic bags can be recycled into new plastic bags, or into fiber to create materials such as polar fleece. It's perhaps not the best reuse, but it is reuse. However, the city does not pick up plastic bags on the curb. The consumer's recycling options are limited; I am fortunate enough to be a member of the Park Slope Food Coop, which will recycle many of these bags.
Now that I have established the potential for the reuse of paper and plastic, we need only implement a system by which these materials are collected. I propose one solution: deposits for paper and plastic. I know this is possible, because they do it elsewhere.
Without doing too much research, I know that there is an additional cost per-bag at stores in France and Ireland. This is a tax to encourage people to bring their own bags, and I think it's great. But what if we could not just implement that tax, but also return it per bag returned? And for the case of paper, what if fast-food restaurants would serve you a burger on a plate, and charge a packaging tax for wrapped food to-go?
It's difficult, but it could make New York cleaner.