I was hunting for such databases for a while while preparing my project. Here is what I collected.
For brain-computer interface developers:
Currently the biggest database for BCI experiments. Contains EEG’s recorded while imagining various movements and P300 data. Also find here desriptions & rankings for different BCI algorithms.
P300 data for 9 subjects and Matlab code to reproduce results of their paper “An efficient P300-based brain-computer interface for disabled subjects”
EEG’s of 2 subjects’ movement imagery
Look here for project’s #8 “Audiovisual Content Generation Controlled by Physiological Signals for Clinical and Artistic Applications” database. It contains EEG recordings for finger, foot & tongue movements.
EEG recordings of 8 subjects while they were asleep
Another sleep EEG but from a heart study. Data from one subject is available for download, another 9736 polysomnograms need to be asked for.
Abnormal EEG from epileptic patients:
EEG recordings from epileptic patients (intracranial) and healthy volunteers
Some VEP, epileptic and control EEG recordings
A huge database containing ~120 subjects, and for each of them, ~120 one-second VEP recordings. Subjects were presented with simple pictures and their EEG was recorded for one second as they looked on the image trying to remember it.
Here you can download 3.4 Gb database with EEG’s recorded for 14 subjects while they perform picture recognition or categorization tasks.
EEG’s from five subjects while they’re trying to distinguish between synonymous and non-synonymous word pairs
EEG recordings of 7 subjects while they perform such tasks as counting, math, rotation, letter writing or just simply resting.
“Emotionally driven physiological signals from both the peripheral (galvanic skin response, respiration and blood volume pressure) and central nervous system (EEG and frontal fNIRS)”. More about the project + source code for data analysis – on eNTERFACE page – look for project #7 in 2006 year results