This is a little more structured that what you may be looking for but for career exploration in middle school, we use Glencoe's Exploring Careers. The text itself is pretty basic and not as useful as it could be. But at the end of each chapter there is a career cluster that lists a lot of different jobs in one area. We have ds13 choose one and research its salary, education requirements, working conditions etc. It helped ds17 figure out what he may like or may not like to do when he did it.
An example of a career cluster and careers:Agriculture, Food, and Natural Resources - Agricultural Scientist, Aquaculturist, Deckhand,Ecologist, Farmer, Forester, Game Warden, Geologist