I've used two previous Twitter integrating plugins both of which have dwindled in development along the way but Wp to Twitter remains fully supported and regularly updated by its developer, who provides superb, responsive support by the way.
This plugin works nicely out of the box and has lots of nice configurable features, but if you really want to set your tweets apart then the pro version is well worth the investment. It allows you to schedule your tweets, repost your tweets up to 3 times and include your article featured images in your tweets! If that isn't unique and special then I don't know what else there is it could possibly do.
The free version is brilliant, the pro version is amazing!