We just changed what is published to Facebook in last post, lets do the same for twitter. I am gonna be layze and just change the original module, but you can build your custom and override it. So twitter module is the module we use and we open twitter_post.module file and edit it on twitter_nodeapi part. It is simple edit, simple additon to code. In replacement array we just add something to sent title, like below
$replacements = array('!title' => $node->title.' - '.$node->field_headline[0]['value'],
there is $node->field_headline[0]['value'] which is just some CCK field I have in my content type, as twitter is just short message, or title with some link, this is what we do, just add that to original node title and this is how we changed it.
Take a file below