ChibiOS/RT is a compact and fast RTOS designed for embedded applications. It offers threads, mutexes, semaphores, messages, events, timers, flexible I/O with timeout capability. ARM7, Cortex-M3, AVR, MSP430 and x86 are currently supported.
FreeOSEK (originally called OpenSEK) is a scalable solution for embedded system. FreeOSEK OS is based on OSEK-VDX RTOS specification and is best suitable for small and fast real time operating systems.
This project provides three different interfaces for programming embedded chips: a GObject based library (for developers), an executable binary (for computer geeks) and a GTK+3 front-end (for less geeky users). Actually NXP LPC and STM32 based chips are supported.