This contribution contains a summary and some highlights from the Photocathode Physics for Photoinjectors (P3) Workshop [1]. This workshop, held at Brookhaven National Laboratory in Ocotber of 2010, was aimed at bringing the photocathode community together to discuss and explore the current state of the art in accelerator photocathodes, from both a theoretical and a materials science perspective. All types of photocathode materials were discussed, including metals, NEA and PEA semiconductors, and "designer" photocathodes with bespoke properties. Topics of the workshop included: Current status of photocathodes for accelerator applications Current fabrication methods Applications of modern materials science to the growth and analysis of cathodes Photoemission spectroscopy as a diagnostic of cathode performance Utilization of modern user facilities Photoemission theory Novel ideas in cathode development Discussion forum on future collaboration for cathode growth, analysis and testing