I've just finished putting the last touches on the Sapphire Hacking Wiki available at:
I urge any new HTC Magic users to read it to help them get started.
I urge any advanced users to read it and help keep it up to date!
This is a generic Hacking guide for any Sapphire handset - ie. HTC Magic, Vodafone Magic, Rogers HTC Magic, Google ION, even the TMobile MyTouch 3G!