Here is a very inspiring article in the NYTimes about urban food production and food sustainability:
StreetFarmer

And Deeaimond-
Here is an amazing website about an urban family who have transformed their 1/5 acre city lot into a self sufficient food garden of eden:
PathToFreedom
They have also started a large website here freedomgardenswhere you can find groups of all kinds of 'farmers'- even apartment dwellers who raise sprouts in tiny boxes or use only pots or window boxes to grow various food. Don't be discouraged no matter how little space you have!
I find these websites very helpful and full of all kinds of ingenious ideas for growing things in clever ways no matter what our home space is like.