So, I'm going to need a compiler and associated tools collectively known as a tool-chain. Easy, GCC, thats that one done, erm.. hang on, on closer inspection there are a number of options available to me all of which are based on gcc in some form or another.
GNUArm : Well the last release was in 2006 and requires cygwin, a linux shell for windows. This rules this one straight out for me as it goes against the K.I.S.S. principle. Why add extra complexity.
Yagarto: which appears to be an excellent open source project, including setup tutorials and a mine of useful links, this is a good contender however there is one more...
Code Sourcery G++ Lite: This is the open source version of the commercial tool chain. Quoting directly from their site "CodeSourcery, in partnership with ARM, Ltd., develops improvements to the GNU Tool-chain for ARM processors and provides regular, validated releases of the GNU Tool-chain. Sourcery G++ Lite Edition supports ARM, Thumb, and Thumb-2 compilation for all architectures in active use, including Version 7 of the ARM Architecture." That statement makes it an easy choice in my mind. The commercial version of the product includes an eclipse based IDE and looks rather nice, however this is a personal project and part of the fun is doing it for little or no cash.