Guest writer
Guest writer is a puddinq plugin that could suit your needs. The setup is simple: create a user role that can edit one post type. The options vary from allowing (un) registered people posting content that is automatically published or after a test of a moderator. Let people register frontend and create edit / posts without seeing the backend or common WordPress login pages.
Core functionality
- Add guest-writer role for specific abilities
- Add custom post-type for specific purposes