I found my rain barrel guy on craigslist. He offers plain black barrels for $15. He also converts them into rain barrels by adding a spigot, overflow, and mesh top. For this he charges $55 for one, $100 for two, or $140 for three. I could probably convert them myself, but I've never been able to find all of the parts needed at Home Depot. It also saves me time to have him just do it. Also, most rain barrels I've found on the Internet and in stores sell for $90-100 for a single barrel!
I installed two more next to the one I had on the front corner of my house. I put Y-valves on the spigots and connected them with garden hose. I had an old hose that sprung a leak. I cut it to length and put female hose connectors on both ends. I did this so all of the barrels would fill and empty at the same time. The alternative is to connect the overflows to each other. Doing that causes them to fill in sequence. The first barrel gets full and then overflows to the second, which then gets full and overflows to the third. I'd rather use all three of them in parallel.
I connected 3/4" PVC pipe to the overflow connectors. I didn't bother gluing the pieces together.
The third barrel went under the down spout next to my driveway. And look at that. There's still enough room there for two more barrels!