I recently found a forked project MSPGCC4. It is built against newer GCC and GDB. It supports multiple versions. I tried GCC 4.4.3 and GDB 7.0.1. The compilation and installation is very easy. Just run the buildgcc.sh, choose wanted versions and watch the progress.
MSP430, GCC, mspdebug
This article describes brief steps to setup a Linux development tools for MSP430 MCU – compiler and programmer. MSP430 is not as well linux-supported as AVR or 8051 but fortunately there are ways to make it working.