General info:

Nearest towns (varies by campus):

• Lands End: San Francisco, CA
• Milagra Ridge: Pacifica and San Bruno, CA
• Mori Point: Pacifica, CA
• Rancho Corrall de Tierra: Montara and El Grenada, CA
• Phleger Estate: Woodside, CA

Regions:

• Lands End: San Francisco & San Pablo Bays
• Milagra, Mori, and Rancho: Pacifica & Half Moon Bay
• Phleger: Central Peninsula & North Skyline

Park websites:

• General overview: Link here; see also here
  
• Lands End: Link here
• Milagra Ridge: Link here
• Mori Point: Link here
  
• Rancho Corrall de Tierra: Link here
• Phleger Estate: Link here
  

Best time of year to visit: Year round
Features of the park: The diversity of the campuses (these are only the ones I have visited!)
Fees: None of the ones that I've been to already have required  fees, but Muir Woods National Monument does.
Remaining GGNRA campuses to visit: Olema Valley, Tomales Bay, Muir Woods, Alcatraz, Bolinas Lagoon, Marin Headlands, Fort Point, Presidio, Fort Funston, and Sweeney Ridge.

Map of GG National Recreation Area

Campuses of GGNRA (click on photos):

Lands End - Presidio

Milagra Ridge

Mori Point

Rancho Corrall de Tierra

Phleger Estate