http://www.pstnet.com/eprime.cfm E-Prime features a graphical "drag and drop" interface for creating simple experiments. For more complex experiments there is E-Basic scripting. Be sure to use E-Prime 2.0 as the older buggy 1.0 is also installed on many university PCs.
http://www.neurobs.com/ Presentation is able to deliver stimuli with millisecond timing accuracy. Presentation is very flexible and can be used to control nearly any behavioural experiment.
NBS training videos for Presentation are on YouTube at http://www.youtube.com/user/NBSTraining
Psychtoolbox (PTB) is a free set of Matlab functions. Matlab and Psychtoolbox are installed on small PC in the scanner suite.
The recommended environment for PTB is GNU Octave running on Ubuntu. Windows and MacOS are no longer supported. MATLAB is supported only on linux. As of August 2017, we are moving to Ubuntu and Octave.
See Porting to Octave for help with common issues when converting from MATLAB.