I've built mine based on the same pid controller, relay and sensor used on the seattlefoodgeek page, but didn't use a imersion heater or a water pump.
For the heating element I used one electric burner (just like this one: http://www.ebay.com/itm/Durabrand-Electric-1100-Watt-Single-Burner-Hot-Plate-Portable-Cook-Range-NEW-/171062487225?pt=Small_Kitchen_Appliances_US&hash=item27d41e68b9). Didn't like the idea of a imersion heater because if it is turned on by accident while out of the water it burns in seconds while the electric burner justs works normally.
Using the electric burner also let me use any pot I have to make sous vide, I just put it on top of the burner as I would normally do if I where cooking without sous vide. This setup allows me to not use a water pump because the convection already takes de hotter water from the bottom of the pan to de top, while bringing the cooler water down for heating (because the heat source is in the bottom, bellow the pot).
For a chassis for the pid, relay and power plugs, I used a tuperware pot.
All in all, it was a very cheap way of getting a very high quality setup.
