If multiple items have the same enchantment, does the bonus stack?

Instances of Fortify X (Where X is "Conjuration, Smithing, One-handed, etc.") stack if they're from separate items.

You cannot use the "Double Enchantment" perk in the enchanting tree to double-enchant a single item with the same enchantment, twice.

Unlike in Oblivion, stacking skills above 100 actually increases their effectiveness.