eCos: An open-source real-time operating system for embedded applications. Site includes news, documentation, downloads, FAQ, mailing lists and hardware compatibility details

L3-L4 Microkernel Family: Lean, with fast, message-based, synchronous IPC, simply-used external paging mechanisms, security mechanism based on secure domains: tasks, clans, chiefs. Kernels try to implement only a minimal set of abstractions on which OSs can be built flexibly. L3 has system-wide persistence

QNX Software Systems, Ltd.: Canadian firm that develops, maintains, and markets QNX RTOS and related products: Photon microGUI, QNX/Neutrino, IAT, FLEET, FTL, QNX In-Hand Toolkit, PhAB, Phindows, PhinX, Voyager. QNX is fast microkernel, POSIX.1 compliant, x86 platform, year 2000 safe