Have you already gone through the links inside Webmaster Tools?
- Go into Webmaster Tools
- Select your domain
- Click the 'Traffic' dropdown, and Click 'Links to Your Site'.
- Under the 'Who links the Most', click 'More »'.
- On this page, you'll want to click the 'Download more sample links', and 'Download latest links' buttons. Save them as CSV, and open them in Excel as soon as they're finished downloading.
This will give you a pretty good export of some of the backlinks Google's referring to. Go through and select a good chunk of them to disavow.