I am not a huge report guy on Google AdSense, but according to a WebmasterWorld thread, Google has added a new filter option on their advanced reports. You can now filter the reports by unit type.
If you want to see how much money you are making from "ad units" versus "link units," you can now easily do that via the "Choose Units" option in the Google AdSense advanced reports section. Here is a screen capture:
Honestly, I would not have known if this option is new or not myself. So I am going by the word of three different WebmasterWorld members, who are reporting it is brand new.
Forum discussion at WebmasterWorld.