SEGGER
Segger develops and distributes software development tools and ANSI C software components for embedded systems. Main products are : emWin, an universal graphics software (GUI) for embedded applications; embOS, a small real-time kernel; emFile, an embedded file system; USB stacks; and J-Link, the JTAG emulator for ARM cores. Segger cuts software development time for embedded applications by offering compact, flexible and easy-to-use middleware.
embOS
Available for CPUs from 8 to 32bits.
Easily portable to any CPU at request.
One of the smallest and fastest kernel available.
No configuration needed.
No royalties.
Profiling support included.
The embOS trial version includes start projects for popular evalboards, the complete documentation, embOSVIEW etc.
Click below for Trial Version
http://www.segger.com/downloads.html