Mike Madden of Gannett News has a brief round-up of the money that was spent lobbying for and against immigration "reform" in 2005 and the first part of 2006 here.
According to a Gannett study, $3.3 million was spent in that period, and most of that was the pro side. They also mention the Center for Responsive Politics. Their raw data is here, but it looks like some of the dollar figures might include all lobbying an organization does, not just that related to immigration.
A sidebar shows some of those lobbying for and against the Senate amnesty. On the against side were NumbersUSA, National Border Patrol Council, U.S. Border Control, and Federation for American Immigration Reform with almost a million total.