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For the legendaries you can browse the game guide. Not sure if they're done updating though. Most websites haven't been updated for 2.0.1 yet, which is mainly because they're all drawing their insights from the official D3 API, and it's just not updated yet, still many bugs as you can see when you visit the armory.
I doubt that any website will have a completely correct set of information about all items before RoS, and once RoS hits they all have to udpate again, so for now I think there's no "one source" to get it all at once. Might have to wait until early April, when the dust of news has settled, all bugs have been fixed, and everything is up-to-date and correct.
I do not have a list or confirmation, but from my play experience (as a wizard) you'll find elemental damage on gear. Such as Fire/ice/Poison/Arcane/Lightening skills dealing +15% damage. There are also spells that increase their damage, such affixes I found were + damage to Electrocute, Arcane Orb, Disintegrate, Blizzard, Hyrda, Spec Blade, Meteor, Familiar, and I'm most likely missing more. But i know all those affixes have dropped for me.
Primary spells ("generators"): pants (I'm sure there's a second one, but can't remember it).
Boots, belt, helmet, chest armor, off-hand, and shoulders can roll skill damage bonus (non-primary skills), and I have yet to see a comprehensive list for each class+skills, but it's usually a set of 4-7 spells per slot per class that can potentially roll, and usually no skill can be buffed by more than two (not sure, can someone confirm this) slots.
No, my question is if a single spell can be buffed on three slots. For example, Blizzard damage bonus can roll on chest and shoulders, Wave of Force on boots and helmet, Meteor on orb and... no idea what else. But are there any triple-buffs for spells, i.e., three slots that can roll that bonus?
Anyways, all this is a pain in the ass to find out now, but super easy come RoS (just ask the Mystic, she'll show you all the stats). :-)