I remember that natural weapons count as light weapons, but I can't find where it says this. Help?
Also, are there any spells or effects, etc. that can change the damage type of natural weapons (like making a bite do slashing damage or whatevs)?
Yeah, the weapon finesse entry is the only mention of natural weapons being light that I know of. Of course, there aren't many other cases where it would matter, so...
As far as damage type changing, I don't know of any off hand. It's a little odd to begin with, since damage type is determined by the type of attack, and not the actual natural weapon used. eg. all Bite attacks are B/S/P, Claw and Talon are S/P, Gore is P, etc.
I'll keep looking though, there may be something that I'm not remembering.