Strength
Strength Governs the Skills of Blade, Blunt, and Hand to Hand. Additionally it determines your total encumbrance (5x Strength) and how much damage your blows do.
Intelligence
Intelligence determines your total Magicka (2x your intelligence) and your total magicka use. Intelligence governs the skills of Alchemy, Conjuration, and Mysticism.
Willpower
Willpower determines how fast your Magicka regenerates. Willpower governs the skills of Alteration, Destruction, and Restoration.
Speed
Speed determines how fast your character moves. it governs the skils of Acrobatics, Light Armor, and Athletics.
Agility
Agility governs the skills of Security, Sneak, and Marksman. Characters with a low agility have a greater chance of getting knocked down.
Endurance
Endurance determines your total fatigue and health (1/4 Endurance added to health every time you level up). Endurance governs the skills of Heavy Armor, Armorer, and Block.
Personality
Personality determines an NPC's disposition towards you and governs the skills of Mercantile, Speechcraft, and Illusion.
Luck
Luck governs no skills, but has an effect on everything that you do