There is a growing chorus these days claiming that trying to find deeply fulfilling work in a recession is like trying to milk a fish.
Consider the recent article "The Most Overrated Careers", where Marty Nemko of US News and World Report highlighted "13 occupations with a mystic that exceeds reality". These include Non-profit Manager, Advertising Executive, Attorney, Physician and Teacher, among others. People are naturally drawn toward these careers because they are passionate about the cause, but often discover the work has downsides that outsiders might not be aware of. The message of the article? Letting passion influence your career decisions can lead you straight into a rut.
But it doesn't have to.
There are two primary factors that define passion in a work environment: Cause and Challenge. Cause refers to your personal alignment with a particular mission. Are you passionate about helping children, or the environment, or medicine or science? Challenge, on the other hand relates to your passion for the work itself - the day to day activities. I once sat next to a man on a flight who had been IBM's general council for nearly 30 years. I asked him, given all that he had seen, what was the part of his career that he looked back on most fondly? "1972!" he exclaimed without hesitation. "We were being sued by the government for anti-trust. We were having all sorts of product and customer problems. The challenge was so exciting!" Work is about solving problems, and just as there are causes that you are drawn to, there are also challenges that you are most excited to tackle.
Reflecting on your passion for both Cause and Challenge allows you to better understand where you are now, and may also indicate where your career should be headed. 
Community - This is the person who joined the non-profit for the cause, but hates the internal politics and barriers to success. You are aligned with the company's mission, but the day-to-day work is a grind.
Strategy: When making career decisions, avoid being blinded by the perception and glamour of a job. Dig into the specifics of the workday, and even consider volunteering first. If already in the job, explore new opportunities until you find the right role within the community you love.
Competency - This is the lawyer who went to law school because that's what you are supposed to do when you gradate high in your class with a liberal arts degree. They joined a top firm because they it was the most prestigious offer. Then they wake up one day, without a passion for the work, and wonder how they ever got on this track to begin with!
Strategy: Just because you are good at it, doesn't mean that is what you are supposed to be doing. Identify areas where you can apply your strengths to causes you believe in. Or, get creative about creating a greater cause for your current objectives (e.g. Dove's Campaign for Real Beauty).
Corrosion - Your lack of passion for the cause is only over shadowed by your incompetency in the role. While you may certainly survive in the role for awhile, over time, lack of passion for what you are doing and what you are accomplishing will corrode your attitude, motivation and performance.
Strategy: Summon the confidence that there is more out there for you. Safely but methodically begin exploring new paths toward activities and outcomes that you are passionate about.
If you understand the challenges that motivate you (and which you are good at), then align them with a cause that gives you purpose. If you have discovered your cause, experiment with different roles until your daily works brings you energy.
And if you currently have neither, rest assured that there is nowhere to go but up.
Are you passionate about your work? How did you successfully steer yourself toward the job?