Superlab Now both Mac & PC
Free experimentation software, for Windows
Mike Ford's DMDX tutorials and links, with sample scripts for various Visual Word Recognition Experiments
Inquisit The World's Fastest Psychological Research Software! Inquisit is a flexible, open-ended, high performance psychological experiment generation tool for Windows 95, 98, and NT 4. Inquisit supports a wide variety of psychological data collection methods, ranging from simple questionnaires to reaction time tasks where every millisecond counts. Inquisit uses state-of-the-art Microsoft technologies, including DirectX for rapid picture presentation and Speech Recognition APIs for identification and timing of verbal responses. Inquisit also makes it easy to selectively demo tasks, trials, and blocks for presentations and lectures.
Psyscope scripts, a long list of scripts related to cognitive psychology experiments of all sorts
Psyscript Experimentation software based on applescript. Now OSX version
Experimental Psychology Software (Mac) by anonymous ftp.
Linger, a software package for performing reading, listening, and other sentence processing experiments. Linger was primarily designed for masked, self-paced reading experiments. Written in TCL/TK, it can run on any of the main platforms