This excellent column by the Post's Sebastian Mallaby is a must-read for anyone interested in the immigration issue. It's far from an exhaustive debunking of some of the nativist myths that float around the ether, but it's a good start.
A caveat: the argument about the cost of undocumented workers to the average family is a bit specious, since it uses averages to ignore the fact that both the tax burden and the fruits of economic growth are unevenly distributed. I would like a more specific study focusing on the effect of undocumented workers on working-class people where the rich's contribution to the tax burden and portion of economic growth is factored out. The rest is pretty well done.