[Clippard has a good selection of solenoid valves.][1]  Their line of inexpensive valves is called [mouse valves][2]. They cost on the order of $25.  I've been using them for years

Clippard makes other types of pneumatic hardware too: cylinders, regulators, gauges, manifolds, fittings, etc.

Here are a few more manufacturers that may be instrumental for building pneumatics: [Beswick Engineering][3], [Norgren][4].


  [1]: http://www.clippard.com/store/byo_electronic/
  [2]: http://www.clippard.com/store/byo_electronic/byo_mouse_valves.asp
  [3]: http://www.beswick.com/
  [4]: http://www.norgren.com/global/