The first part of finding the optimal career for you is figuring "you" out. Without stepping back and taking a good look at who you are as a person, and what you enjoy doing, it's really hard to figure out what you'll enjoy doing for the next 30 years.
Yet too many of us (especially scientists!) think that self-evaluation is a waste of time. We rush around, from one degree to another, from one alternative career to another, unhappy but without really understanding why.
The award-winning Career Development Manual  from the University of Waterloo tries to change that. It's not so much of a Web page or information center as it is an exercise manual or framework for evaluating one's self.
The manual identifies six steps to a successful and rewarding career and presents them in an easy-to-use, quick-to-print "pyramid" to career planning success. With each level of the pyramid, there are less exercises to do, as you start to understand who you are, what the best career for you might be, and how to move forward in that direction. The first step, "self-assessment," is one of the hardest, but most rewarding, things a scientist can do--use a very straightforward, objective test to get at your most inner feelings. It sounds flaky, but actually printing out and filling out the exercises can be quite draining, as you start to learn, assess, and evaluate, your own goals, values, and interests. I suggest doing only one of these per day, as it will help you to keep thinking about the questions and issues that are raised while you're doing other things. I know you could do the whole step in about 10 minutes, but avoid the temptation. Take time to mull things over.
The next step of the pyramid, "occupational research," gives you ideas and a regimented approach to understanding what, exactly, the day-to-day activities of a job might be. Is it something that will be rewarding to you, based on your self-evaluation in the last step of the pyramid?
Decision-making, the third level of the pyramid, makes you think about your career objectives, your goals and aspirations, and other long-term choices like your social and emotional needs. Again, sounds hokey, but not enough people do it. Why be stuck in a job you hate just because you didn't think about the fact that you needed a dynamic atmosphere?
The "employment contacts" level of the pyramid features a very well laid out and organized template for resumes, job interviews, and the like. Hey--you study for a test, why not an interview? Again, don't just read through the section, print it out and give the answers (the spaces left blank on the sheets) some serious thought.
The last two levels of the pyramid discuss ongoing things to be done or thought about, after you've gotten your "ideal" job. Read them at work! Hey, if it really is your ideal job, the boss won't mind.