MSPGCC is a freely available, community-supported compiler for MSP430. It supports ALL released MSP430 devices. This is a great alternative for commercial tools, such as IAR or CCS. The community has just released a new BETA that expands support for devices with memory more than 64 KB (20-bit support/CPUx).
This is a command line compiler and it is available on different host operating systems, such as Windows, Linux and even Mac OS!
Give it a try, or even contribute to this open source project! More information found on the MSPGCC SourceForge page.