Dunno if its already posted here, but there is a way to get Guild Experience really really fast without playing Rated BG, doing tons of quests, or having a guild hero daily.
If you´re playing usual BG with 2 guildgroups of min. 4 men, and join twin peaks/ws or Battle for Gilneas the BG is rated as a GuildBG and gives you and your guild really fast the Guildcap for the day ;-) and the Randoms are mostly 3-0 win (works best in BfG)
Furthermore you get Reputation for your Guild(dunno exactly but about 200+ for each BG)
All you have to do is, communicate in Ts3 or else, if your invite plops exactly in the same time than the invite of your 2nd guildgrp and join, otherwise do not and do it as long as you have an invite at the same time ;-)