resources.py

class ProfileResource(ModelResource):
    user = fields.ForeignKey(UserResource, 'user')

    def prepend_urls(self):
        urls = [
            url(r'^(?P<resource_name>%s)/(?P<username>[\w\d_.-]+)/$' %\
                self._meta.resource_name, self.wrap_view('user_by_username'),
                name='profile_user_by_username')
        ]
        return urls

    def user_by_username(self, request, **kwargs):
        response_class = HttpResponse
        try:
            user = User.objects.get(username=kwargs['username'])
        except User.DoesNotExist:
            data = []
            response_class = HttpResponseNotFound
        else:
            bundle = Bundle(user, request=request)
            data = UserResource().full_dehydrate(bundle)
        finally:
            return self.create_response(request, data, response_class)