The American Constitution Society for Law and Policy offers in PDF format a comprehensive index of presidential signing statements issued between 2001 and 2007. According to the Society's Web site, "the index, compiled by Neil Kinkopf, associate professor of law at Georgia State University College of Law and former special assistant in the Office of Legal Counsel at the Department of Justice, provides a comprehensive list of every provision of a law objected to by the White House in a signing statement, the reason for the objection, and a link to the relevant signing statement".
In addition, the index assigns each objection to one or more categories, from a base set of twenty-three. These categories include constitutional, doctrinal, structural, and other justifications for objection.
Ernster, the Virtual Library Cat