PLR stands for Private Label Rights and there are a lot of uses for this type of material. What you want are exclusive (limited) PLR deals that are only sold to a small number of people before the offer is pulled. The biggest percentage of buyers will never follow-through with the material they purchased (sadly), so the content is relatively unique.
With Private Label Rights you can change anything you like about the content, sign your own name to it, put a new cover graphic on it, basically do whatever you can dream up with it. Its different than resale rights, which you do not have rights to edit/change.
I have a package called PLR VooDoo that is free to download in the Elite Members area (the Private Forum) for anyone that has access.