FieldTrip provides support for data files from CTF, Neuromag, BTI/4D-Neuroimaging, Yokogawa, BrainVision, Neuroscan, EEProbe, BESA, Neuralynx, Plexon. Note that new dataformats are being added all the time, so the information here might be outdated. There is a separate page on supported data formats, please look there for more details.