Here are a few more sources of data that might be interesting for you:
http://wiki.gephi.org/index.php?title=Datasets — right off of the Gephi download page, it has a fair amount of overlap with Newman’s collection of networks but also includes some cool ones such as a graph of Github users.
http://snap.stanford.edu/data/index.html — these data are probably not very good for this assignment, since they are quite large. However, if you’re interested in large-scale data, this is the place to find it.
If you find other data sources, please share them with the class in the comments section!