apt-get install binutils-msp430 gcc-msp430 \ msp430-libc msp430mcu mspdebug
There's one annoying bug in Oneiric's version of binutils-msp430 which breaks build with -ffunction-sections -Wl,--gc-sections options (which is kinda common trick in embedded world to remove unused functions and reduce code size): mspgcc #3386145. It is fixed in Ubuntu 12.04 (Precise).
I'm however still running Maverick, so instead I downloaded following Oneiric packages:
binutils-msp430_2.21~msp20110421-2_i386.deb gcc-msp430_4.5.3~mspgcc-4.5.2-20110612-1_i386.deb libgmp10_5.0.1+dfsg-7ubuntu2_i386.deb libmpc2_0.9-3_i386.deb msp430-libc_20110612-1_i386.deb mspdebug_0.16-1_i386.deb
Then few from Precise:
(If you try to install Precise versions of other packages on Maverick, they want to pull upgrades to system libs, which I wanted to avoid).
and installed them manually with dpkg.