Need Web service/application that's kinda a survey tool?

What’s a good Web service or application for collecting form data that providers can periodically update themselves, and then give others password protected access to view/search the form data in aggregate?

I’m looking for a way—maybe using a wiki or similar service—to allow one set of users to create a basic profile with username and password, and then respond to a series of form questions that they can periodically update using their username/pwd—then allow another set of users to view/search all of this data from multiple providers? The second set of users must have a username and password too to specifically view the data provided by others.

I’d rather not commission someone to build this application but am not sure what already may exist to do these things—I guess it’s almost like a survey builder where responses can be updated by survey taker later, then a way for someone to view survey results later.

Thanks for any suggestions!