As some of you may know, there is a version of the SigmaTel SDK floating on the net. It isn't too old, i think it'll be of some use as it is mainly for the STMP35xx chipsets.
But to me it just looks like a big load of junk. There's no proper documentation, no newbie stuff (guess those firmware developers actually know how to code :lol

. The file that was of most use to me was the PDF with the detailed description of the chipset's insides. :P
It's basically a collection of C++ and ASM scripts thrown in a crapload of folders, there seems to be some sort of compiler too but it ain't very helpful. My C++ knowledge is pretty limited and i know next to nothing about ASM coding, not to mention it ain't x86 ASM, as what makes the SigmaTel chipsets tick seems to be a Motorola core.
If anyone wants to give it a spin i'll upload it here.