Civil Air Patrol
CAP is also very good for networking. And not to say KFAHMI is wrong, but there actually is a program within CAP that allows cadets to earn their private through CAP (only cadets, not senior members). And KFAHMI is right about it being an efficient and economical way to build time, and stay current. The last time I checked, the glass C182 went for $50 dry.
As far as the resume goes, it is considered an volunteer service, so it couldn't hurt to add it.
Good luck