After looking online, I found this: http://forum.northernbrewer.com/viewtopic.php?f=3&t=61167&sid=f054f78a221afd9740f0c31521c11bc4 , which really helped me with the basics and why not to use brass/copper. His design is pretty great, but I think I have been able to simplify and make it cheaper.
Step 1: Gather Needed Materials
2 1/2" threaded to 1/4" push to connect
1 1/4" to 1/4" push to connect
1 1/2" threaded to 1/2" barbed fitting
1 1/2" Brass Tee
Some 1/4" Ice maker tubing
1' Length of vinyl tubing (not pictured)
I think I spent just around $25 on parts (if that much).
You are a going to need a drill, 1/4" bit and an adjustable wrench
Step 2: Drill Out One of the 1/2" Threaded to 1/4" Push to Connect
Flip it, so the threads are facing up and look for the hole on the inside, you need to open that hole to 1/4 inch. Its at maybe an 1/8" or 3/16".
Keep in mind there is an o-ring in there that has to stay intact.
If you do this right, you can now pass the 1/4" tubing through there and maintain an airtight seal.
Step 3: Assemble the Tap
The 1/2" threaded to 1/4" you did not drill is your input for your gas side.
Run a good length of tubing through the modified fitting, so you have maybe 18" of tubing coming out of the bottom of the tee and leave about 2" on the outside.
Run the 18" of tubing through the barb fitting
Teflon tape the threads, and be very careful when you thread them on; they will strip easy. Don't over tighten.
Step 4: And Done
Check all your connections with soapy water.
I am using my regulator from edge star (see my other instructable, link on the cover page), so I that is why I went with 1/4" tubing for my gas line, when I get a second regulator I may have to change this out. For my faucet, I just used a cobra tap stepped down to 1/4" and I was set.
Toss your mini keg in the cooler and you are ready to rock!
With the cooler I had, I did have to drill a hole and have my co2 tank on the outside, since it wouldn't fit standing up.