Google Ferric Chloride... Radi Shack sells small bottles, but they can be had in 1-gallon jugs online practically everywhere.

Some more helpful hints from someone who has been there:
1) The paper listed is good, but needlessly expensive. Pick an inkjet paper that has a high clay content, higher the better.
2) Agitate the board constantly, an aeration tube for fishies works well
3) If possible, keep the board verticle while etching. This typically requires a custom-built etching tank, useful if you plan to do this form time to time.
4) Warm the etchant (another use for fish tank accessories, the heater), but don't get it too hot (no boiling)... about warm enough for a hot bath.
5) Continually check board to prevent undercutting lines with etchant... expect a cold solution to take 10-20 minutes to etch, warm will do it in 5-10.
6) Dispose of FeCl[sub]3[/sub] properly (local landfills typically accept this stuff on certain days of the week). This stuff will etch away your copper pipes (duh!), will kill a lot of good chemicals in the local water treatment plant, and if you do it often enough can make men with chemical smapling gear appear in the sewers outside your home and eventually your door!




And when you've had enough of messing with chemicals.... send the boards off to a proper board house and be done with it

 

My 2 cents:
This technique works well. Additional hints:
Lacquer thinner/remover will allow you to recycle the boards if you don't get a complete transfer. Sometimes you can't get the whole pattern to transfer. Once you make up a pattern, print a dozen or so on the inkjet paper, so you won't waste time or paper if it doesn't work the first time. Just wipe it off and give it another try.

You might be able to repair bad traces (one's which didn't transfer) with just a regular Sharpie type of ink pen before etching. I've been able to use them, and they are readily available and don't have to cost a lot. Just experiment on a spare board before you commit your design to the etching.

Cleaning the board with a mildly abrasive process helps the toner stick.

After transfering, there is some residue, which I think is the plastic from the toner, that you need to rub off, otherwise your board won't etch properly. I usually can rub it off with my finger under a stream of water.

If you mount a Dremel tool to your drill press (or get one of those adapters to make a drill press out a regular drill) and use some of those cheap carbide drills from Harbor Freight (50 or so for a few dollars), you can drill the holes for your components. I also tried mounting a small laser to help me zero in on the holes.

I got my ferric chloride at RadioShack.

Overall, I think it's a great process. Doesn't require a darkroom and revisions are almost as simple as revising a drawing on your PC.

Now that I think of it, I also used this technique for a non-PC board project. I made a woodworking plane with brass and steel and I was able to transfer my design to the brass before cutting by ironing on the design.

You can also use this technique for transfering the component locations on the reverse side of your PCB, before or after etching the copper traces. Takes a little of the mystery out of where to put the parts after making your board.

 

If you plan to drill more than a few holes (20+), don't get the cheapy carbon bits... the fiberglass wears the edge down quickly and you'll start to rip the copper away from hole edges, especially the smaller holes with thin annular rings (the surrounding copper). The titanium coated are better, but not ideal...