wp-postratings: list current user’s unrated posts

The best approach would be:

  1. Get an array of all of the post IDs in the database.
  2. Get an array of all of the post IDs that the user has rated (as you have done in your example)
  3. Remove the IDs in step 2 from step 1 – you’ll then have an array of all unrated post IDs by that user.