Speech

Haggling

 * You've learned how to deal with Skyrim's greedy merchants and how to haggle for better prices.
 * Effects: buy and sell prices are improved 1% per your Speech level.

Silver Tongue (25 Speech required)

 * You've spent quite some time improving your rhetorical skills and are now able to greatly influence any conversation and to fascinate the opposite gender. You also get better offers at respective vendors.
 * Effects: player intimidation multiplied by 3. Sell/buy prices improved by 10% when you're trading with opposide gender.

Merchant (50 Speech required)

 * Your trading skills are good enough to sell almost anything to any merchant willing to trade with you, and you can invest some of your gold with a shopkeeper to increase his available gold permanently.
 * Effects: sell prices increased by 15%. Player now can give 500 gold to merchant to increase his gold. Every merchant will buy anything (not stolen) regardless of his profession.

Leadership (75 Speech required)

 * Your rhetorical skill makes you the perfect leader. By inspiring all those who fight by your side, you encourage your followers to always push their abilities to their very limits.
 * Effects: damage with all weapons increased by 20%. Conjuration, Alteration, Restoration, Destruction spells cost 15% less mana. Amount of blocking damage increased by 75%. Magicka and Stamina increased by 100. Magicka and Stamina regeneration increased by 50%. Carry Weight increased by 50.

Fencing (100 Speech required)

 * You've become so persuasive that you could make almost anyone believe that your goods are of a legal origin.
 * Effects: stolen items can be sold to any merchant.

Masquerade (100 Speech required)
Rank 1: Rank 2:
 * You've become proficient at acting, and with the right equipment you can now disguise yourself, although sometimes people can still tell that you are not truly one of them.
 * Effects: allows the Player to wear other faction armor to become undetected. The following factions are referenced: Forsworn, Imperial, Necromancer, Stormcloak, Thalmor, Warlock.
 * There is no role you cannot play, and your acting is so believable that there is almost no way for others to see through your disguises.
 * Effects: improves the effects of the perk. (?)

Lore of the Thu'um

 * You've been studying the lore and ancient script of dragons and the Thu'um. Thus, you can shout more often.
 * Effects: improves Shout recovery by 10%.

Destructive Urge

 * The horrors that the Thu'um can inflict are etched on your mind just as you have seen them etched into stone. Your Thu'um will wreak even greater havoc among your unfortunate foes.
 * Effects: if you talk to Paarthurnax and meditate on the 'Yol' word, all your shouts have 15% increased magnitude.

Indomitable Force

 * You know what it means to be called Ysmir, Dragon of the North. As you have withstood the test of Thu'um, so will you withstand the Thu'um of others.
 * Effects: if you talk to Paarthurnax and meditate on the 'Fus' word, you take 50% less damage from enemy shouts, and the duration of their effects is reduced by 50%.

Spiritual Equilibrium

 * You have been guided in meditating on the Thu'um. Now your shouts linger, lasting longer than they did before.
 * Effects: if you talk to Paarthurnax and meditate on the 'Feim' word, the duration of effects caused by your shouts is increased by 15%.

The Way of the Voice

 * You've meditated thoroughly, and acquired vast insights into the Way of the Voice. Thus, you can call upon the power of your Thu'um rapidly once per day.
 * Effects: gives you a power that allows you to shout without cooldown, once a day. The power lasts 5 seconds.

Tongue's Insight

 * You've spent time meditating on the Way of the Voice, unearthing more knowledge and gaining valuable insights. Thus, you can harness the might of yet another word of power.
 * Effects: by taking this perk, you gain one free Dragon Soul. You can repeat the process as long as you have perk points to spend.

Other useful info about Shouts
The Indomitable Force perk makes you resistant to Unrelenting Force, but doesn't make you immune. However, you can gain immunity, and also immunity to the Disarm Shout. Each shout has 3 ranks, and different creatures possess different ranks. Below are some requirements to make you immune to each shout.

Unrelenting Force

 * Rank 1 - knocks you down and deals 20 damage when you have 25 magic resist or less AND 250 health or less. It means that when you get either 26 magic resist OR 251 current health (not base), you will stop the effect.
 * Rank 2 - deals 40 damage, needs more than 35% magic resist or more than 400 health to be resisted.
 * Rank 3 - deals 60 damage, needs more than 50% magic resist or more than 600 health to be resisted.

Disarm Shout

 * Rank 1 - needs more than 25% magic resist or more than 250 current stamina to be resisted.
 * Rank 2 - needs more than 35% magic resist or more than 400 current stamina to be resisted.
 * Rank 3 - needs more than 50% magic resist or more than 600 current stamina to be resisted (apparently this version is NOT used by Dragons, so should apply to Draugr/Wrathmans etc).

NOTE: This information has NOT been confirmed and may not be accurate, according to recent user reports on Reddit.