Reacently I find a very **broken link removed**.(free and open)It is a new, free and highly-integrated software development environment for ARM cortex M3 and M0 based microcontrollers, which includes all the tools necessary to develop high-quality software solutions in a timely and cost effective manner. It integrates CoBuilder and CoDebugger for simplicity and ease of use.
Supported Device:Atmel Energy Micro Luminary NXP Nuvoton ST
Features:
Free to use
-Full functional IDE
-Component-oriented development platform
-Internet-based, efficient integration of network resources
-Integrates CoOS
-Peripheral registers
It's really great ,and I'd like to share with you .You can have a try.