Here's some handy info... again, you'll notice the lack of reference to numbers. There really is a metric crap-ton of useful info in the main forums if you don't mind the slog through all the data. (this is specifically for defenses I believe)
(Disclaimer: copied from the main CO site)1) Innate Bonuses
Every stat provides some sort of benefit to your character. These are described in game and you can place your cursor over the stat in your Character window to see how much of a benefit they provide to each thing. These benefits are the same for everyone, regardless of powers. Here is the list:
Strength
Increases Knockback strength for all knockback attacks.
Increases resistance to Knockback.
Increases ability to break from tangible holds.
Increases melee damage (excluding Ego Blades). The damage bonus caps at 20% and should be easy to reach without Str as a Super Stat.
Increases the weight that can be lifted by "Pickup and Throw" ability.
Constitution
Increases hitpoints.
Ego
Increases critical strike damage.
Increases ability to break from intangible holds.
Ego does NOT universally improve the strength or duration of holds. Confirmed by a developer here.
Recovery
Increases Energy Equilibrium
Increases the percentage of your Total Energy gained when using Energy Building attacks, requiring fewer attacks to reach full Energy.
Dexterity
Increases critical strike chance.
Increases effectiveness of stealth powers.
Intelligence
Reduces Energy costs.
Reduces cooldown times.
Increases Pet damage.
Increases stealth detection.
Presence
Increases threat in Defensive role.
Decreases threat in Offensive and Support roles.
Increases Pet health.
Increases Healing and Buffing effects.
Endurance
Increases maximum Energy.
Increases the numerical amount of Energy gained by Energy Building attacks, but you still take the same number of hits to fill your Energy.
2) Power Bonuses
Certain powers are made stronger by certain stats. They will list the effect in the description. Here is a list of which powers scale based on which stats:
Electricity
Electric Form
End - Increases Energy damage (Electricity, Sonic, Particle) buff.
Rec - Increases Energy damage resistance.
Fire
Fiery Form
Pre - Increases Elemental damage (Fire, Ice, Toxic) buff.
Rec - Increases Elemental damage resistance.
Force
Personal Force Field
End - Increases the amount of damage the force field can absorb.
Ego - Increases the amount of health the force field regains every 3 seconds.
Ice
Ice Form
End - Increases Elemental damage buff.
Dex - Increases Elemental damage resistance.
Archery
None
Gadgeteering
None
Munitions
Holdout Pistol
Dex - Increased damage when landing a critical hit.
Killer Instinct
Dex - Returns Energy when you land a critical hit with a munitions power.
Ego - Increases the amount of Energy returned by critical hits.
Power Armor
Invulnerability
Str - Increases the fixed damage reduction.
Con - Increases the percentage damage reduction.
Martial Arts (Claws, Single Blade, Dual Blades, and Unarmed)
Lightning Reflexes
Dex - Increases dodge and avoidance.
Telekinesis
Telekinesis (the power)
Ego - Increases the size of objects that can be lifted and damage done.
Ego Form
Con - Increases damage reduction.
Ego - Increases the damage of second blade.
Ego Surge
Ego - Increases the damage of second blade.
Telepathy
None
Might
Defiance
Con - Increases defense gained.
Enrage
Str - Increases damage buff.
Darkness
Shadow Form
Con - Increases defense gained.
End - Increases damage buff.
Sorcery (all)
None
However, Int increases pet damage and Pre increases pet health, heals, and buffs. This set is almost entirely pets, heals, and buffs.
Supernatural
Regeneration
Con - Regeneration does NOT heal based on total health, CON has no impact on this power. You can see my test results here.
Rec - Improves the regeneration rate.
Dex - Is NOT supposed to allow Regeneration to crit, confirmed by a developer here.
Resurgence
Con - Resurgence appears to heal based on total hitpoints, so higher Con indirectly improves Resurgence.
3) Super Stats
Lastly, you will choose 2 super stats at 5 and 13. These two stats will be granted a bonus every level (at level 40 you get +80 to each super stat). These two stats also provide a bonus to damage for ALL powers. If I chose DEX and CON and had 100 of each, I would do just as much base damage (with the same powers) as someone else who chose EGO and END with 100 in each. The key is deciding which Innate bonuses and Power bonuses are important to you and then choosing your two super stats based on how you want your character to perform. I'll give you another example:
My main character is a Mentalist who uses a mixture of Force/Telekinesis/Telepathy powers, including Personal Force Field. I choose EGO and END for my super stats, as a result I get the following bonuses from these two stats:
EGO
-Increased inmaterial hold resistance (Innate)
-Increased Critical hit damage (Innate)
-Increased PFF absorption regen (Power)
-Increased Telekinesis strength (Power) -- That is the Telekinesis power for lifting objects, not the whole Set
-Increased base damage on every damage power I have (Super Stat)
END
-Increased Total Energy (Innate)
-Increased Energy from Energy Building Attacks (Innate)
-Increased PFF total damage absorb (Power)
-Increased base damage on every damage power I have (Super Stat)
At the same time, I could take DEX instead of END to build a "critical hit" type character, but my Personal Force Field and Total Energy would suffer because I would be more focused on DEX gear. I can still get the DEX +critical with END as a super stat. But since I'd lack the +DEX super stat bonus, and I'd focus more on END gear for all of its benefits, my critical chance would not likely be as high.
edit: stuff... like spelling 
