Openforis

this is a set of modules that enable remote authentication between Drupal and non Drupal sites. Openforis is a server to provide this service, utilising the Services module.

There is also a client module so that your site can communicate to the server, making it possible for one server to support multiple sites. This model will work between Drupal and non-Drupal sites provided they are compatible with Services module. The project page also states that cck profile fields can be used, which would provide even greater interoperability with systems where you have to use a non-drupal application’s fields.

Articles: 
Modules roundup 1 year 10 weeks ago
External Links: 
Project page