From PrestoPundit:

Rich folks with illegal nannies and servants are getting services without paying the true cost of labor -- in other words, illegal immigration is providing a government subsidy for the pampered lifestyles of the well to do. It is doing the same for wealthy firms of all sorts -- from agribusiness to international hotels to Walmart. The market tells us that the value of this illegal foreign labor is no more than a pittance -- indeed at the margin a good deal of this labor would be replaced by improved capital goods or simple technological innovation, if our borders were secure .. and if the government subsidy for this labor didn't exist...

He also links to this report:

"Based on estimates developed by the National Academy of Sciences for immigrants by age and education at arrival, the lifetime fiscal impact (taxes paid minus services used) for the average adult Mexican immigrant is a negative $55,200...

This reduction in wages for the unskilled has likely reduced prices for consumers by only an estimated .08 to .2 percent in the 1990s. The impact is so small because unskilled labor accounts for only a tiny fraction of total economic output."

See also his post about Immigration and class warfare:

If the American people are against massive illegal immigration why are politicians, academics and the media for it? Answer? This is class warfare folks, and the elite classes in America are after privileges and power they can't have without the moral power they gain from paternalistically "caring for" an ever growing poverty class -- and the material privileges they can enjoy from the dirt cheap labor immigrants can provide scrubbing the floors, cleaning the pools, raising the kids, building the second homes, clearing the tables and cleaning the toilets, etc.

(See the discussion of the Ford Foundation's ties with the UCLA voting-for-illegal-aliens study here.)

He has more on the Bush/Fox Amnesty here, here, here, here, and here. Scroll backwards for even more.