There is lots of control subject MRI data (structural and resting state fMRI) in the NITRC Image Repository (http://www.nitrc.org/ir/app/template/Sea...) some of this is completely open access (i.e. 1000 Functional Connectomes, IXI dataset, CANDIShare, Study Forrest), much more data is available from other projects that require registration (which can often be quite simple).

More generally, searching NITRC for the 'Data' keyword (i.e. http://www.nitrc.org/search/?type_of_sea...) provides lots of leads for other potential data sources.

If you can be more specific about what you're looking for, perhaps someone can give you some more specific leads.