Setup passes were introduced at the end of 2012 (as simply "Passes"), and explained in more detail in both Hockey Prospectus 2013-14 and Hockey Abstract.
Setup passes are defined as those passes which result in shots on goal, and can help determine which players are most adept at setting up shots in a way that's independent of shooting percentages.
Unfortunately this statistic is not recorded by the NHL (or anyone else). It is therefore available only as an estimate based on the player's (primary) assists and the average shooting percentage of his linemates. To some people that's a tremendous turn-off, even among those who think the concept is excellent. If you are of that mind, think of it only as a handy re-presentation of primary assists and on-ice shooting percentage.
The attached spreadsheet has the raw data and the formula, which has been refined since its initial introduction. There are further refinements in the works, including one based on all attempted shots (Corsi) and one that correctly removes the players own shots from the on-ice shooting percentage.