FreeRTOS

FreeRTOS
Portable, mini realtime scheduler (RTOS kernel); how to make full embedded solutions on Windows host with quality open source tools, low cost hardware; supports ARM7, PIC18, 8051, Atmel(Mega)AVR, RDC8822 (AMD AM186 clone), PC with DOS. [Open Source, GPL]
http://www.freertos.org/

FreeRTOS
Growing article, with links to many related topics. Wikipedia.
http://en.wikipedia.org/wiki/FreeRTOS

FreeRTOS Real Time Kernel
Project page: news, forums, support, CVS, bug reports, feature requests, statistics. SourceForge.
http://sourceforge.net/projects/freertos/

Wittenstein High Integrity Systems
High integrity engineering design, development, production; focus: software, safety critical engineering of software and systems; makes and supports FreeRTOS variants SafeRTOS, FreeRTOS-pro. Bristol, UK.
http://www.highintegritysystems.com/