Depends a lot on your personal inclinations, personality, and existing skills, and whether you want to travel a lot or not. Resources you can check out:
1) US Department of Labor (dol.gov) has a lot of web resources on occupations not in demand and ones in demand by region and nationwide, occupations expected to be in high or low demand for the next 10 years, etc.
2) You can also google for articles on occupations in demand - house builders, air traffic controllers, nurses, truckdrivers, railroad workers, industrial plant workers, machinists and industrial plant machinery/equipment operators and mechanics are among those with very high demand right now, largely due to "aging out" of a significant portion of the existing personnel.
3) Your local state job service/employment office has resources and commonly weekly orientation seminars on job hunting, how to find occupations in demand, etc.
4) Some state job services and many community colleges give occupational aptitude tests for free or quite cheap every few months - a few hour written test that determines, commonly quite well, what types of work you are inclined to like or be prepared for. The Armed Services Vocational Aptitute Battery (ASVAB) test also does a pretty good measurement of what types of work you appear to have an aptitude towards (but unlike the tests above, does not really measure how much you would "like" that type of work). Given by the military recruiting centers and periodically at schools - no charge, but does mean your name is in their lists so you will get some junk recruiting mailings now and then from them, but a good assessment of where your existing skills or abilities might place you in work.
5) Skim through the want ads in local paper - the bigger the ad and the more for a certain skill, the greater the demand is for that type of worker.
6) If in high school or college, your School Counseling and Advising office has lots of resources on various trades and occupations and the training/education needed for each. Also college catalogs and guides like the Peterson Guides listing hundreds of schools by location, size, programs available, etc. Ditto for public library - commonly has many of same resources but not in as great a quantity.
7) My recommendation - skip the web technical institutes and such and "work at home" scams. Find a field you want to work in and get an entry level job or go to school for entry-level training, then work on-the-job for awhile to determine first whether you really likethat trade or tuype of work or not and the customer contact (or lack thereof) associated with it, then decide it you want to up-school to move up in the business, or move up through the ranks to the point where you can become your own boss.
8) Also, on the "own boss" thing - bear in mind if you intend to run any sort of a company beyond say a one-man handyman or yard care service or such, you will be getting involved in a pretty fair amount of bookkeeping and keeping up with tax withholding and tax payments and insurance and such - so if you are not inclined to that sort of deskwork, consider that in choosing a "career".
