We are not so "meta" today, and more hands on.
Given the spam avalanche today, with people trying to get me to use a webapp that checks "who within my firends does not follow me" - I thought: That is quite easy -- just pick one set of people and subtract from the other, and voilá!
To get it out of terminal usage, I added in a little bit Tkinter - it is quite minimalist, still the Tkinter Part could contain some interesting patterns that I had to look around to produce (like, using the scrollbar, or updating what is displayed on teh window in the middle of data processing, with the tk.call("update") thing )
As for th twitter, we are not using any libraries exteranl to Python - just the rest API for a service that does not need authentication, and good old "urllib". We just loop through the follower and friends page results, and handpick just the users screen name (we could pick URL, and others for a more sofisticated app).