Equipment Manufacturers:
Arri Camera - Film and Digital Cameras and Lighting
Aaton - Film and Digital Cameras and Audio
Bolex - Yes they still make Bolex cameras
Panavision - Film and Digital Cameras
Red Camera - Digital Cinema Cameras
Silicon Imaging - Digital Cinema Camera
Sony - Digital Cameras
Panasonic - Panasonic Digital Cameras

Cooke Optics
Motion Picture Lens Database - Richard Bradbury

Film Manufacturers:

Professional sites and lists:
CML - Cinematography Mailing List
The ASC - American Society of Cinematographers - Cinematography Discussions
Pro Video Coalition - Lots of articles and tests
Creative CowForums - The answers can be found here
Screen Light and Grip newsletter - Electric explanations
Digital Cinema Society
SMPTE - If you don't know, then check it out.

Rental Houses NYC:
Cameras Service Center - Arri Owned Rental house
Panavision - If you want Panavision
Abel Cine Tech - Camera Sales, Rentals and Support
LVR - Camera and lighting Rental
Du-all Camera - Used/New Sales, Rentals, Service
Pro-Sound - Audio Used/New Sales, Rentals, Service