Asaph has probably the most elegant bookmarklet ever for posting things. It doesn’t have a ton of options, but when you just want to post something, it just works, and works well.
http://www.phoboslab.org/log/2008/04/asaph-1-0
I definitely think there is something there for MT to look at.
Reported on Movable Type 4.2
It's a great example, and thanks for pointing it out. We actually have something similar we'd done in the labs for Vox, and we'll see if we can bring a nice javascript like that over to MT in the future. If you're inclined, it also sounds like it'd be a great hack to contribute to MTOS! :)