But a substantial fraction of the responders won't have a computer - I want to find that - or are barely computer-literate.
Alright then, how about telephone IVR.... get a company to host a button push survey for you.... this can be magically compiled into a database form... you can even give people a PIN number to login.
Otherwise heavy-duty OCR made by the likes of Kofax or Visionshape is probably what you're after, preferably (but not necessarily if you're willing to put up with a trade-off on the speed/quality side of things) combined with a decent document scanner.
Or just make sure your forms are correctly designed for optimal high speed scanning and then outsource the post-processing, the latter being able to advise on the former. Depending on the nature of the forms, perhaps a company such as Popularis might suit (not a recommendation, just used by a company I deal with who I know have used them for a few years now).