A cheap 3-way valve becomes much more useful when it is actuated by a servo! Use this as part of an elaborate aquarium air system, a component in an automatic watering scheme, or to switch intake/outlet for a syringe pump (like this Thing: http://www.thingiverse.com/thing:866904).

Thanks to Nordson Medical for the samples to develop this!

Still in progress since the spacing for the raw valve and the cover are not quite right. But you can file it to fit.

Print one of each part. It's a good idea to test fit things and trim or file to fit. I had to trim a bit off the corners of one of the mounting brackets on my servo, and had to file a bit to make the little valve fit when I put the cover on it.
Hardware:
1 three-way valve. I used Nordson Medical FCLBFFM-1A-003. They were good enough to send me a sample, but I haven't found a source for these where I could order less than 100. If you know of such a place, please post. Similar three-way valves will likely work.
1 servo with fittings. Use whatever horn allows you to screw on the Valve Drive.
3 10mm (min) x M3 screws to hold the Valve Body Case and the Valve Servo Case together.
2 10mm x M3 screws to hold the Valve Cover on.
2 10mm (min) x M4 screws to hold the servo in.
2 M4 nuts.

Assembly:

Use an M3 tap to tap the holes in the Valve Body Case for the Valve Cover and the holes in the Valve Servo Body for the Valve Body Case.

1. Align the servo so it is centered (at 90 degrees).
2. Screw the Valve Drive to the Servo horn so the valve handle fits into the Valve Drive when the handle is centered. The handle should be a snug slip fit.
3. Slip the valve into place on the Valve Body Case with the handle centered. Put the Valve Cover on and secure it.
4. Mount the servo into the Valve Servo body.
5. Put the Valve Body Case into place with the valve handle in the Valve Drive.

Have fun with your new valve!