I'm hoping for an IDE of some kind, but I'll take any compiler or assembler! Can't seem to find anything by googling.
There is an IAR compiler for download from TI. The free one is code-size-limited. It comes with some kind of IDE as well. But MSP programs are pretty small by definition, and a simple makefile is all you need to compile and program code.
at sourceforge you can find both mspgcc (mspgcc.sf.net) and mspgcc4 (mspgcc4.sf.net). I had trouble recently building mspgcc on a modern Linux (finally did succeed), but mspgcc4 builds just fine no problem.
If all you need is an assembler and linker for now, it is somewhat trivial to cross compile gnu binutils. ./configure --target=msp430 --prefix=/opt/msp430 or something like that.
Also, out of the box, llvm includes the various targets, unlike gcc you do not pick one target when compiling the compiler. The downside is that llvm's msp430 support is considered experimental (as in we probably wont bother with the bug reports). And you will still need binutils to assemble and/or link.
I use Rowley CrossWorks. It's very good, with excellent support.
just recently there was a new release of mspgcc, dubbed temporarily "uniarch", here are som installation instructions for ubuntu
i think that all the recent devices are supported in that version...
my setup is a vmware machine running ubuntu server 11.04, with netatalk and ssh... so with my mac, i connect with terminal over ssh, and mount the ubuntu drive over afp with netatalk... so I use xcode as the development ide, and run the commands on terminal.. it's SO comfortable...
i also have a rakefile that does all the handywork (which can be found in the above repo), and thus I only 'rake mcu=msp430g2211 build install' and it compiles, links and installs on the launchpad...