From publisher blurb:
Crafts and professions are useful skills for just about any player, but where exactly do players go to master their chosen fields of expertise? Adventure Havens: Guild Houses offers twelve ready-to-use guilds for your d20/OGL games. Each guild is fully developed with a detailed history, important NPCs, and story seeds that can be easily folded into your game.
Do you have a player that needs to visit the mage's guild to learn new spells? Is your rogue looking for a discreet place to pick up more caltrops? Does your warrior need access to a forge to craft his new blade? Don't just hand-wave these details. Make them part of the game the way they should be!
Besides the guild information, you'll also find new rules for crafting masterpiece items. Your players will want to learn how they can benefit from these exceptional items.