Programming Language Trends
One idea that "The Passionate Programmer" recommends that I've always been intrigued by is the idea of mapping hot technologies along an early, middle and late adoption trend and seeing where the technologies you work with fall. It is a subjective exercise but does help you think about what is out there. Turns out for programming languages (not frameworks or toolkits) TIOBE Software has for some time now been producing a Programming Community Index that ranks programming languages. They have a methodology that I'm inclined to call good enough for most cases.