Slipperman's Recording Distorted Guitars From Hell
I finally got around to dumping the mp3's at the end of this onto my iPod, and I'm listening to them from work. Not only is the pages and pages of text that predicate it pretty damned phenominal, the audio is pretty great too (though he wanders a lot, although oftentimes his diversions seem more valuable than the actually topics).
Basically, if you record heavy guitars, you should read this, even if you eventually end up disagreeing with him. Knowledge is power.