How to install GNU ARM toolchain on Ubuntu 11.10?

You should be able to use the binary distribution provided by gnuarm.

http://www.gnuarm.com/support.html

Or you can build from source -- there is a script to do this for you here, though it is a little old -- you may want to alter the download links
http://blog.nutaksas.com/2009/05/installing-gnuarm-arm-toolchain-on.html

Of course you will need some way to program your embedded device (ie in order to load the cross-compiled binaries into your chip), which is sorta covered here, but is specific to your programmer device and ARM chip.