MeshNetics - 802.15.4 / ZigBee Wireless RF Modules
MeshNetics is a creator of easy-to-integrate 802.15.4 / ZigBee wireless RF modules and ZigBee PRO-certified mesh networking software, used by OEMs and system integrators to add wireless connectivity to their products and solutions. MeshNetics RF modules feature industry-leading range performance, long battery life and ultra-small footprint. They are designed for use in 868/915 MHz and 2.4 GHz frequency bands. MeshNetics is a single source of ZigBee modules, development tools, networking software, technical support, and design services.

Mocana NanoSSH Embedded SSH Client & Embedded SSH Server

rtos    

C/OS-II
µC/OS-II, The Real-Time Kernel is a highly portable, ROMable, very scalable, preemptive real-time, multitasking kernel (RTOS) for microprocessors and microcontrollers. µC/OS-II can manage up to 63 application tasks. Over 100 microprocessor ports available to DOWNLOAD.
preview: http://www.micrium.com  

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avr-rtos
A Real-Time Operating System kernel for the Atmel AVR microcontroller, incorporating tasks, memory management, semaphores, queues, and other features
preview: http://sourceforge.net  

rtos    

AvrX Real Time Kernel
AvrX is a Real Time Multitasking Kernel written for the Atmel AVR series of micro controllers. AvrX contains approximately 40 API in the following Six categories: Tasking * Semaphores * Timer Management * Message Queues * Single Step Debugging support * Byte FIFO support with synchronization. The Kernel is written in assembly. Total kernel size varies from ~500 to 700 words depending upon which version is being used.
preview: http://www.barello.net  

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FreeRTOS - Realtime Scheduler
Portable, open source, mini Real Time Kernel - a free to download and royalty free RTOS that can be used in commercial applications. FreeRTOS is licensed under a modified GPL and can be used in commercial applications under this license. (Supports ARM Cortex-M3, ARM7, ARM9, HCS12, H8S, MSP430, Microblaze, Coldfire, AVR, x86, 8051, PIC24 & dsPIC.)
preview: http://www.freertos.org  

rtos    

XMK - eXtreme Minimal Kernel
XMK is a preemptive multi-tasking kernel for 8bit microcontrollers. Its goal is to provide a bare bones RTOS with a small enough footprint (RAM+ROM) to run on 8bit microcontrollers. Open Source RTOS for 8Bit microcontrollers - Including Hitachi H8 and Atmel's AVR chips.
preview: http://www.shift-right.com