If you're interested in creating your own online experiments, the source that I found most valuable was a pair of books by Michael Birnbaum:

Birnbaum, M. H. (2000).  Psychological Experiments on the Internet.  Academic Press: New York.

Birnbaum, M. H. (2001).  Introduction to Behavioral Research on the Internet.  Prentice Hall: Upper Saddle River, NJ.


Web sites with information on creating online psychology experiments:

• Birnbaum's home page .  Includes links to experiments, software, etc.

Web sites with more psychology experiments:

(Please note that these sites do not give receipts for participation, so you cannot get extra credit for them.  Some of them do offer payment, or chances to win prizes.)

• Birnbaum's experiments (mainly on decision making).
• Psychexperiments at Ole Miss.
• John Kranz's "Psychological Research on the Net" .
  
• UCSD Attention and Perception page.
• Behavioral Decision Research lab at the London School of Economics.
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