The bonus includes adventuring, AA, crafting, and guild experience.
Announced on EverQuest2.com:
Adventure, Tradeskill, AA, and Guild XP will be doubled from 12:00pm (Noon) PDT on Friday, July 19 through 11:59pm (Midnight) PDT on Sunday, July 21, 2013. Take advantage of this limited time offer and watch those XP bars fill up!
Enjoy doubled adventuring, alternate advancement, crafting, and guild experience. The bonus weekend will run from 12pm (noon) Pacific Time on Friday, July 19 and will conclude at 11:59pm Pacific Time on Sunday, July 21. If you have a Gold membership, don't forget to kick in your daily "Gold Rush" buff!