TinyOS is an event-driven operating system for networked applications in wireless embedded systems, with a component-based architecture. It is based on the nesC programming language and its core components require only 400 bytes of memory (data and instruction). While TinyOS is sometimes considered a de facto standard, Contiki has a much easier learning curve for the developer, since it is based on a NesC programming language. This article will deal with how to instal TinyOS and how you can build your own application. Other areas include

 Hardware Primer
 Basic nesC Syntax
 Advanced nesC Syntax
 Network CommunicaAon
 Sensor Data AcquisiAon
 Debugging Tricks and Techniques

Full tutorial here --its FREE & Ur welcome!
http://www.wsnmagazine.com/tinyos-tutorial/