The Panamanian Tourism Authority, ATP, is Panama's official tourism organization. Its website (www.visitpanama.com) is an excellent pre-trip planning resource with overviews of Panama's regions and points of interest.
ATP has 17 offices around Panama, open weekdays 8–3:30. The English-speaking staff at ATP offices are friendly and helpful. Their resources—mostly brochures—tend to plug local tour companies rather than aid independent exploration.
Other resources include The Visitor, a small, free paper found at most hotels and travel agencies, and Panama Planner, an excellent tourism magazine, available at large hotels.