The EFM32 chips are something to look at in the ARM arena. They’re easy to develop with and the less expensive starter kit can be used as a development platform and a programmer/debugger for projects. If you’re doing an energy harvesting or battery powered project and need an ARM micro the chips work well since they’re designed for energy efficiency.
Just as much as the chips, look at the tools they are giving away! The Simplicity Studio has everything you can think of in terms of short cutting design times ‘Designer’ and the energyaware ‘Profiler’ gives the ability to debug real-time development code for energy efficiency. This is the kind of tool support that either you needed $1,000 hardware or $1,000 tools, fair play to Energy Micro and the EFM32, it just set the new benchmark for others to follow!