Once you've discovered (or rediscovered) your passion, spend some time researching the types of careers that center around your passions.
Don't worry if you're feeling a bit unsure or insecure -- it's a natural part of the career change process. How much research you do also partly depends on how much of a change you're making; for example, changing from a teacher to a corporate trainer versus switching from a nurse to a Web designer.
You can find some great career information and a skills-matching service at O*NET Online from the U.S. Department of Labor. The O*NET system serves as the nation's primary source of occupational information, providing comprehensive information on key attributes and characteristics of workers and occupations. It also has some great questionnaires that can be used by employers as well as someone trying to find a job. So explore the site and take advantage of all the free resources.