Mining-the-Social-Web (Python)
github.com
github.com
Of course, when you're ready to graduate, look into Lucene & Mahout for some heavy duty stuff. If you want to make any of these map-reduce'able, Yelp's Mr. Job (also Python) is a handy tool.
On top of that, the BackType blog is always full of gems. Their recent dissection of the #lessambitiousmovies trend on twitter was quite interesting (http://blog.backtype.com/2011/01/analysis-of-the-lessambitio...)