Netnewswire-twitter is a project mainly written in ..., it's free.
Script for posting whatever you're reading to Twitter via Twitter.app
Simple apple script to post from NetNewsWire to Tweetie.app by using the "twitter://" url schema. Script basically taken from TwitNews and changed to work with Twitter.app instead of own scheme.
URL schema documented here.
Just check out and call
make allAnd it will compile the script and copy it to the NetNewsWire script folder.
Please check the wiki for info.