Urban Maple Syrup
The Heavy Table just did a post on a woman making maple syrup from the trees in her yard in Minneapolis, which I think is awesome. You can even learn how through the DNR which has been offering workshops at some State Parks (including Fort Snelling) about how to make Maple Syrup (as of 4/1 the workshops were starting to wrap up with the end of the season but there's still a few left further north in the state).
It got me thinking about an idea I had awhile ago - why not create a sugar shack in the city? It would take some work but I think it would be worth looking into. You could make artisan syrup and sell it locally. Transportation costs for your finished product would be small and you could even do sap collection via human powered transport, enabling you to establish some green cred. The most difficult thing might be getting access to enough maple trees within a reasonable distance of the shack, but perhaps that could be made possible through agreements with home owners. Even better, set up the shack as a co-op and allow members to get a certain percentage of production based on how many trees they contribute to the effort or how much sap is collected from their trees. If only I had more time I'd be all over this.