And provided you want to go the cross way, like ixtab said, a Linaro or CodeSourcery TC is probably the easiest thing you can get your hands on, and, if you're only targetting the K4/K5, it usually works well enough without too many hair-pulling experiences
.
I personally am building two different TCs with the help of crosstool-ng, one targetting the K2/K3, and the other the K5. I'm using bleeding edge GCC versions, so there is some hoop jumping to be done, especially for the K3 toolchain. My configs & build-scripts are available in the kindle-x-tc-YYYY.MM.tar.gz attachement of the
gigantic K2/K3 hack threads.
There are a *lot* of different ways to do it, and each of us tends to do our "own" stuff, so there isn't a really universal 'right way' to do it. For a cross TC, I'd say the closest to it would be the CodeSourcery TC, a recent one for the K5, and the truly awfully old one from 2009q7 (I think?) for the K3.
If you have more specific questions, don't hesitate to ask, or to come looking for us on IRC
.