One of the things that WoW uses in it's simplest form is the "hardcore quests" (or high-level quests). Adventures targeted to high-level characters, usually requiring special equipment (which means raiding again and again dungeons to get...
Gamasutra has finished posting the 3-part special of the History of Computer Role-Playing Games. It is an amazing work and anyone who likes rpgs should read it (beware, more than 100 pages printed ;) Click on the images to read each part: