Wow...
Blitz finally pointed out a thread I could post in, where I actually felt comfortable talkin' about this kinda stuff.
System of a Down are definitely a great band, just because they're so unique. I currently prefer their self-titled release, only because I've heard it so much and I think it's a little more diverse musically...
As for other 'nu-metal'...
Deftones - As previouslly said, but I prefer Adrenaline too. It's just so much more classic.
Cold - An alternative to Staind, they're more doomy and the guitars are more effects based giving them a more eerie feel.
Mudvayne - Awesome nu-metal with a great Bassplayer who goes nuts, but believe me, it takes AGES to get into them.
Skinlab - Bay Area band that sounds a lot like a nu-er version of Machine Head. Very good with a meaty vocalist, and some trippy skrape effects on the guitars.
Other bands:
Soulfly, Dry Kill Logic, Ill Nino, Poison the Well, Godsmack, Static-X, Disturbed, Sevendust, Nonpoint, Powerman 5000, [minus], Drowning Pool, Alien Ant Farm, Finger11, Project86, LostProphets, Spineshank, Taproot, AmberVoid, Chimaira, Vision of Disorder, 36 Crazyfists, Erase, The Dillinger Escape Plan, Mr Bungle, Fantomas,