In World of Warcraft: Cataclysm, a new Guild Leveling System will be implemented, consisting of 25 levels total.  Each level provides a Perk for all guild members. 

Gaining guild experience for the guild will happen when you do certain in game functions with a group that is comprised of at least 75% guild members. 

Experience for your Guild is also earned through Guild Achievements.  The harder the difficulty of the Achievement the more experience it will yield for the guild. 

Guild Reputation will be required to use some of the Item Perks you can recieve as your Guild advances.   An example: You can buy an addition Heirloom item only available through a Guild, you'll need reputation in order to purchase the helmet.  Guild Reputation gains are gained through quests and achievements, but the amount of reputation you get is based on how much Guild Experience the quest or achievement gives.

Guild Reputation is unique in that it's not like other factions throughout the game.  It was tweaked to specifically not be something you can just grind out.  That said, it will take effort to raise your guild reputation. 

The Guild Reputation System and Guild Level System were implemented to promote cooperative gameplay amongst guild mates.  That said, the Reputation and Guild Experience gained while playing with guild mates is greatly increased when more of the guild members are present in a party.

Currently, the reputation cap is set at 9,000 per week.  Once you've hit that cap, you won't be able to recieve anymore reputation til Teusday at 3a.m. 

Level	XP Required	Icon	Spell	Description
2	~16,570k		Fast Track (Rank 1)	Experience gained from killing monsters and completing quests increased by 5%.
3	~18,230k		Mount Up	Increases speed while mounted by 5%. Not active in Battlegrounds or Arenas.
4	~19,890k		Mr. Popularity (Rank 1)	Reputation gained from killing monsters and completing quests increased by 5%.
5	21,550k		Cash Flow (Rank 1)	Each time you loot money from an enemy, an extra 5% money is generated and deposited directly into your guild bank.
6	~23,210k		Fast Track (Rank 2)	Experience gained from killing monsters and completing quests increased by 10%.
7	24,880k		Reinforce (Rank 1)	Items take 5% less durability loss when you die.
8	26,530k		Hasty Hearth	Reduces the cooldown on your Hearthstone by 15 minutes.
9	~28,200k		Reinforce (Rank 2)	Items take 10% less durability loss when you die.
10	~29,850k		Chug-A-Lug (Rank 1)	The duration of buffs from all guild cauldrons and feasts is increased by 50%.
11	~31,510k		Mobile Banking	Summons your guild bank. Instant, 1 hr cooldown
12	33,170k		Mr. Popularity (Rank 2)	Reputation gained from killing monsters and completing quests increased by 10%.
13	~34,830k		Honorable Mention (Rank 1)	Increases Honor points gained by 5%.
14	~34,490k		Working Overtime	Increases the chance to gain a skill increase on tradeskills by 10%.
15	38,140k		The Quick and the Dead	Increases health and mana gained when resurrected by a guild member by 50% and increases movement speed while dead by 100%. Does not function in combat or while in a Battleground or Arena.
16	39,800k		Cash Flow (Rank 2)	Each time you loot money from an enemy, an extra 10% money is generated and deposited directly into your guild bank.
17	41,450k		G-Mail	In-game mail sent between guild members now arrives instantly.
18	~43,110k		For Great Justice	Increases Justice points gained by 5%.
19	~44,770k		Honorable Mention (Rank 2)	Increases Honor points gained by 10%.
20	~46,430k		Happy Hour	Increases the number of flasks gained from using a flask cauldron by 100%.
21	~48,100k		Have Group, Will Travel	Summons all raid or party members to the caster's current location. Unlimited range, 6 sec cast / Channeled, 2 hr cooldown
22	49,750k		Chug-A-Lug (Rank 2)	The duration of buffs from all guild cauldrons and feasts is increased by 100%.
23	~51,410k		Bountiful Bags	Increases the quantity of materials gained from Mining, Skinning, Herbalism, and Disenchanting by 15%.
24	~53,070k		Bartering	Reduces the price of items from all vendors by 5%.
25	~54,730k		Mass Resurrection	Brings all dead party and raid members back to life with 35% health and 35% mana. Cannot be cast when in combat. 64% of base mana, Unlimited range, 10 sec cast