The AFL-CIO pioneered union research in to the exercise of shareholder voting rights by fund managers in the mid 1990s. You can find their latest proxy voting survey here.
They were followed by the Canadian labour movement whose annual proxy voting survey is produced by SHARE. The 2006 survey can be found here.
Most recently the TUC joined the club in 2003, and its latest voting survey can be found here.
Since the introduction of mandatory public disclosure of voting record in the US there have been more specialist surveys focusing on particular types of resolutions. Both the AFL-CIO and their affiliate AFSCME have produced very interesting reports on the voting of mutual funds on executive pay.