Sites devoted to specific brands or OSs such as Nokia, Symbian, Windows Mobile, Palm, Blackberry, Android or Maemo.
Android

News, reviews and software about and for Google's open source Android mobile operating system.
iOS

Mobile sites dedicated to the iPhone, iPod Touch and iPad including iPhone news and fan sites,iPhone modding, jailbreaking and hacking and IPhone user forums.
BlackBerry

Windows Phone

Sites for and about Windows Phone and legacy Microsoft Smartphone and Windows Mobile devices and apps.
Meego - Mer - Jolla

MeeGo was a joint venture by Intel and Nokia to create a next generation open source mobile operating system for phones, netbooks, tablets and devices like navigation systems and TV set top boxes.
Nokia withdrew from the project in February 2011 and then released the last and only MeeGo phones the N9 and N950. Intel renamed the project as Tizen in September, 2011. Tizen replaces Qt with Web technologies and targets the same platforms as MeeGo. Development of the original MeeGo codebase continues as a community project under the name Mer. Jolla which will will launch its first phone in 2013 is based on Mer.
Here are some mobile sites covering MeeGo and its successors.
Nokia

Sites covering Nokia phones and software with news, reviews, downloads and forums
WebOS/Palm OS

Sites covering phones running WebOS or the legacy Palm OS