http://www.android.com/ Android is an operating system for mobile devices such as cellular phones, tablet computers and netbooks. Android is developed by Google and is based upon the Linux kernel and GNU software. It was initially developed by Android Inc. (a firm later purchased by Google) and lately broadened to the Open Handset Alliance.
http://www.microsoft.com/windowsmobile/en-us/default.mspx Windows Mobile (rebranded as Windows Phone with the launch of Windows Phone 7) is a mobile operating system developed by Microsoft for use in smartphones and mobile devices. It is designed to be somewhat similar to desktop versions of Windows, feature-wise and aesthetically. Additionally, third-party software development is available for Windows Mobile, and software can be purchased via the Windows Marketplace for Mobile.
http://www.limofoundation.org/ The LiMo (Linux Mobile) Foundation is an organization aiming to establish a globally competitive, Linux-based mobile operating system for smartphone mobile devices. It was founded in January 2007 and has more than 50 member organizations. Backing from major industry leaders puts LiMo at the Heart of the Mobile Industry and makes LiMo the unifying force in Mobile Linux.
http://www.styletap.com/ StyleTap Platform is a Palm OS simulator/compatibilitylayer/emulator for the Windows Mobile/Windows CE and Symbian OS operating systems. It emulates Palm OS 5.2 platform and earlier. Applications written for Palm OS platform show up as native Windows Mobile-based Pocket PC and Smartphone programs and operate in the same way.
http://maemo.nokia.com/ Maemo is an advanced Linux-based operating system designed to run on high-end Nokia mobile computers. As this is an open-source platform, it enables the Maemo community to freely modify and continually develop software as part of a shared goal: to bring added value to all Maemo users.
http://meego.com/ MeeGo is a Linux-based open source mobile operating system project which was announced at Mobile World Congress in February 2010 by Intel and Nokia in a joint press conference. Its aim is to merge the efforts of Intel on Moblin and of Nokia on Maemo into one project. It is hosted by the Linux Foundation. According to Intel, MeeGo was developed because Microsoft did not offer comprehensive Windows 7 support for the Atom processor.
http://www.blackberry.com/ BlackBerry OS is a proprietary mobile operating system, developed by Research In Motion for its BlackBerry line of smartphone handheld devices. The operating system provides multitasking and supports specialized input devices that have been adopted by RIM for use in its handhelds, particularly the trackwheel, trackball, and most recently, the trackpad and touchscreen.
Access Linux Platform
http://alp.access-company.com/ The Access Linux Platform (ALP), once referred to as a next-generation version of the Palm OS is an open source-based operating system for mobile devices developed and marketed by Access Co., of Tokyo, Japan. The platform includes execution environments for Java, classic Palm OS, and GTK+-based native Linux applications.