MissionPilots.org has Pilots positions available for Pilot time building on its single-engine and twin-engine aircraft in both a volunteer Pilot and Co-Pilot positions, on a position-reservation and financial donation basis.
These volunteer Pilot and Co-Pilot positions are offered on a first come, first served basis - you need to reserve a position (if available) and donate money to reserve a pilot position.
http://missionpilots.org or contact [email protected]