PsychoPy is an open source software package that that allows for the presentation of stimuli and collection of data for a wide range of neuroscience, psychology and psychophysics experiments. It is largely platform independent - running on Linux, Windows, and OS X. 

Support for the development of PsychoPy has come from the HEA Psychology Network, Cambridge Research Systems, University of Nottingham, BBSRC, and the Wellcome Trust.

PsychoPy is used by many labs worldwide for psychophysics, cognitive neuroscience and experimental psychology.