IGDA Casual Games SIG White Paper

The International Game Developer Association Casual Games Special Interest Group released a 2005 Casual Games White Paper back in July. Since educational games are unlikely to compete against top-shelf commercial games, the "casual games" market has a lower barrier to entry, and business models will be closer to that of casual games than commercial games, much of the information out there on casual games can be applied to educational games, so it's worth a read.