I compiled a list of skill affixes for better readability. All of them are datamined, so they may be inaccurate. I only included the highest level affixes on the list.
All of the skill bonuses are suffixes, so only one can spawn on a Magic item. Rare items are a question mark in this regard, because we don't know enough about the item generator. It's possible, that the number of skill affixes is limited to one even on Rare items.
These affixes start appearing on class-specific items in Nightmare and on generic items in Hell. What's interesting is that some of the highest level affixes can't spawn on the most powerful class-specific items, because their item level isn't high enough, but they can spawn on the generic items with the highest level. I hope this will change.
Code:Item Group 1: Spirit Stones, Helms Item Group 2: Staves, Polearms, Daibos Skill Bonus May Spawn on Item Group Crippling Wave +5-14% Inreased Damage 1 Cyclone Strike Spirit Cost Reduced by 1-5 1 Deadly Reach +5-14% Inreased Damage 1 Exploding Palm +5-14% Inreased Damage 1 Fists of Thunder +5-14% Inreased Damage 1 Lashing Tail Kick Spirit Cost Reduced by 1-5 2 Sweeping Wind +5-14% Inreased Damage 1 Tempest Rush +2-8% Critical Chance 2 Wave of Light +2-8% Critical Chance 2 Way of the Hundred Fists +5-14% Inreased Damage 1