Included with the upcoming World of Warcraft 4.1 update are Guild Challenges, a new feature that rewards extra guild EXP and gold. To be eligible for Guild Challenges, the guild must be at least level 5 and participating members must have honored reputation within the guild.
How do you take part in Guild Challenges? Simply have a certain amount of guild members present for dungeons and battlegrounds: three members for dungeons, eight for battlegrounds, and 20 for raids. Once the challenge is met, the guild is awarded the EXP and gold is directly deposited into the guild vault.
Best of all, Guild Challenges award EXP beyond the daily experience cap so your guild can level up quicker if everyone puts in a fair share of effort. If your guild hits the level cap, Guild Challenges will simply award even more gold.
Source: Battle.net