Mark did blog about Quickfile just a few days ago. Coincidence? I don't know but the only that is tru as that I'm in love with it as it fill one of the blannk left in Thunderbird list of features compared to KMail. In KMail you do that with the 'M' key. I can now file messages quickly without using the mouse. I still miss the manual filtering like Evolution and KMail provides...

Off course since Mark paid a bounty for it, it is in Dapper:

apt-get install thunderbird-quickfile