Manufacturer Developer Programs

Most mobile phone and mobile device manufacturers offer developer programs with services like news, forums, and device documentation. Some of the better ones have loaner devices for testing.

BenQ - BenQ Developer Portal - (formerly Siemens ICM Portal)
BlackBerry - BlackBerry Developer Program
Danger - Danger Developer Zone
Ericsson - Ericsson Mobility World
Motorola - MotoDev - Offers a device loaner service.
Nokia - Forum Nokia
Openwave - Openwave Developer Network
Samsung - Samsung Developers Club
SonyEricsson - SonyEricsson Developer World - Top-tier site with docs, tools, forums, news, etc.