here is a link to archigrams website,
I have been researching them for my dissertation and thought it might be of benefit to the group work. They did a lot of proposals for new cities including the plug in city, living city, walking city etc. Some of there stuff looks at mega structures, plug in city was an adapatable mega structure where new units were 'plugged' in, which might be an interesting take on the whole neighbourhood block. It might seem a bit unrealistic for what we are aiming to do but its worth a look. They have some pretty amazing images as well, drawings, collages etc. if thats all we take from it. There is also a book in the library called Archigram, Architecture without Architecture, which is probably better if you are looking for images.