I have a patch that adds functionality for Reddit here: http://www.codemonkeyramblings.com/2008/08/reddit-patch-for-actionstreams.php. Instructions for integrating it are at my blog. Works for me, and hopefully will help others.
Reported on Movable Type 4.2
Nice work!
It may be worth pointing it out to Mark Pasc as he is good at integrating these things into the main Action Stream core. Either that or you could package it up as it's own plugin, which is fairly easily done.