45 or 60 watt soldering iron.
0.032" diameter (or so) rosin core solder
This step takes about 3 or 4 hours. It's very unforgiving. If you have never soldered before, you should get help with this. The ground plane doesn't have "thermals", so it takes some heat to melt the solder to it. Check out this help file for soldering the control board. See pages 2 through 19:http://www.paulandsabrinasevstuff.com/EVstuff%20info/Kit%20Assembly%20Directions%20Updated%20March%204,%202010.pdf
Watch for solder bridges (when big globs of solder bridge isolation gaps). Also, you may want to socket the ATMega168. You can program the ATMega168 in-system. So, you can solder it in, and then program it if you want to. Or you can get one preprogrammed.
This video walks you through soldering the control board from start to finish: