UFFS: Ultra-low-cost Flash File System, designed for NAND flash working in embedded system. UFFS typically consumes less then 200K ram for 1Gb(page 512)/4Gb(page 2K) NAND flash. It supports direct flash interface, works with or without OS.
Ivmuk-OS is small RTOS for microcontrollers with low resources. Microchip's PIC16F877A MCU uses about 70 bytes of RAM and 800 bytes Flash. Memory usage depends on number of tasks and messages defined. This should create competition to Salvo OS some day.
Blob is a boot loader for SA11x0 (StrongARM) platforms. Blob is
able to boot a Linux kernel stored in flash or RAM and provide that
kernel with a ramdisk (again from flash or RAM).