EVA Robotics - Tiny stepper drives with servo like performance. Use a small encoder on the motor for positional feedback.
Geckodrive - Compact stepper and servo drives. Also a very good resource for technical information on theory of steppers and power supplies. (UK and Australian agents also available.)
Ocean Controls - Australian supplier of wide range of electronics, stepper motors and drives.
US Digital - For many years the prime source for reasonably priced optical encoders and electronic gadgets. Cheaper non-optical encoders are starting to appear though... look for CUI AMT102 as used by Evodrive...
Stop Motion Pro - Software used for Mary & Max and Aardman Studios in the UK.
DragonFrame - Stopmo capture software from the US with lots of cool features for controlling lights etc. Now also with fledgling motion control module. Well integrated for simple stopmotion animation but does not allow realtime operation or previews.