I've finally got around to sorting out my Little Twit site. It now has its own URL and a proper background service that does the scanning (long lived threads in ASP.NET are frowned upon, so it needed to be a Windows service, technical-blah-blah-blah, etc...)
Little Twit lists all the available Twitter names of 1, 2, 3, and 4 letters in length (all the 4's is still scanning at the moment). The list is dynamic, so it either shows you what it has so far or the last complete scan, if it has made one. It is designed to help people looking for short Twitter names (just in case that wasn't obvious).
The service uses the Twitter REST API, but I notice that some supposedly taken names have no corresponding user page. They are in some sort of deactivation limbo I guess.
One interesting thing I noticed was that the number of two-letter names was about 44 when I started (about a month ago), and now it is down to 16 (0j 0q 0y 3o 4y 5j 5v 6l 6o 6y 7p 7y 8h 8k 8w 8y). If I could be bothered I would record and chart the trends, but I'm not sure it would tell you anything more than I have too much time on my hands.
Its just for fun, but suggestions are welcome.