here is my exact setup:
first the co2 tank: ($70 shipped) http://cgi.ebay.com/Catalina-CO2-5-lb-Cylinder-Tank_W0Q...QQrdZ1QQcmdZViewItem
this is a 5lb tank. for my 30 gallon aquarium, this usually lasts about 6 months between refills. it will come empty, and you will have to find someone locally to fill it for you. my guy charges 6 bucks a fill. you can check at welding supply stores and paintball stores and usually you can find someone to fill it. if you can't find anyone, go to google.com and click on the local tab. type in your location, and do a search for "welding" and you might find some good places to call.
second, the controller and regulator:
in the aquabotanic store, robert sells regulators:
you can also pruchase them on ebay.
the milualkee regulator just screws in to the top of your co2 tank. be sure to use a wrinch so that it is extra tight. once it's hooked up to a full tank, you will want to close the needle valve and the front black knob all the way. you then open the main knob attached to the tank all the way open. this sets the seal and makes it air tight you then open the needle valve all the way. you can now add water to the bubble counter. then slowly turn the black knob until you get bubbles coming out. you can adjust the needle valve (smallest knob) until you get a good flow rate. from the bubble counter, you will attach some sort of air tubing. you can use regular aquarium air hose, or you can get specialized co2 leak proof tubing.
as for the ph controller, the instructions that come with it are very good, just follow them and you will be fine. it should come with everything you need.
now all you need is a reactor:
you can get all types of reactors. what reactors do is mix the co2 into the tank water.
these can be purchased all over the net, but again, robert sells some good stuff.
hope this helps, and as always, if i missed anything, feel free to ask any of us.