OpenSecrets.org provides us with the top 101 All-Time Donors in American Politics from 1989 to 2008:
The most interesting ones to me are the NAR at #3 and AT&T at #1, as nobody else is particularly surprising. Notice that both split between the two parties pretty evenly. I can't help but wonder how NAR's lobbying efforts relates to the housing bubble (Freddie Mac weighs in at #75 on the party fence). I assume AT&T was still recoiling from the Bell System Break up in 1984.
Hat-Tip: Jason Oberle, who passes along the data in a spreadsheet.