The plate is 1/2" thick aluminum. From the bottom I milled off 1/16 inch to countersink an aluminum cover over the water channels. The channels were milled with a 1/4 inch end mill and are about 5/16 inch deep, so the liquid is about 1/8 inch from the top of the plate. The spacing between the channels is about 1/4 inch except for the middle which is slightly thicker to allow room for screws to help hold down the cover plate.
Permatex Blue RTV was used to make the cover waterproof:
Here is a picture with the cover plate installed:
The holes in the sides were tapped using a 1/8"-27 NPT tap and the barbs were purchased off Amazon. They came in a pack of 10 and were relatively inexpensive. I think this is the link:
http://www.amazon.com/dp/B008TSWWAG/ref=biss_dp_t_asn
The pump is a Swiftech MCP655-B, which I purchased a couple of months ago when it was on sale. The price has gone up since then:
Swiftech MCP655-B 12 Volts Industrial Pump MCP655-B - Micro Center
The tubing will depend on the fluid but I am planning on using nylon or silicon. I am thinking about using a standard mix of water and car anti-freeze. It gets cold here, occasionally well below 0F, so freezing is definitely a concern.
Unfortunately the controller isn't installed yet so I really can't say if the water cooling works.