Although I was not a part of this site at its onset, I was the primary maintainer for a number of years. During my time working on it I added several additional experiments and surveys to it.
The Synesthesia Battery represents a significant advancement in psychological research. While many experiments are performed in person with relatively small numbers of test subjects, the Synesthesia Battery is able to deliver interactive psychophysics experiments over the web and has been used to collect data from tens of thousands of subjects.
Of my additions my favorite was the absolute pitch test. Starting from a only request to add such a test, I familiarized myself with the relevant papers and set about producing something that resembled as closely as possible the test originally described in the literature. The main difference of course was this new version was delivered over the web instead of locally on an Apple II computer.