We have found the best place to find barrels is on craigslist.com. Do a local search for "rain barrel" or "water barrel" You'll find a few suppliers in the Jeanette area with pretty fair prices. We bought both of ours for $12 each, they met us in Greentree for the exchange. If you're local to Pittsburgh, you could try calling Delallo's on rt 30.
You'll also need one of these:
As for the spigot installation, you'll need a basic spigot that looks like this:
(the water is draining out of this one because I had just moved it to take its photo)
Drill a hole that is just about the width of the spigot, I think ours was an inch, and I'm fairly certain this is an industry standard size, you'll have to make sure though as you'll want the spigot to screw into the plastic barrel and be quite snug. Once you drill the whole and screw in the spigot, you'll have to get INTO the barrel, to snug it up and to put plumbers putty/glue or tape around there to seal it. That's where the TWO people come into play, one of you will have to hold the barrel in place, while the other wiggles into the barrel. I would also suggest, that if you're the barrel holder, laughing at your partner while they struggle to get into an olive barrel and NOT roll away is not appropriate until after they are OUT of the barrel! I speak from experience!
This is what our barrels look like:
I hope this all makes sense! It's quite an easy project and it's very fulfilling. Nothing like watering your garden with free water right? Please feel free to ask me any questions about the process! I'm happy to help.