Blondguy, while I agree that people don't want their personalities to remain static, I do believe that most people settle into one of the 16 types once they develop later in life. If you are constantly self improving, you might not fit as well into one of the types. However, I use MBTI more of a measure to understand other people quickly instead of introspect on myself and what is my 'true type.'
If you are interested in figuring out what your true type is though, you would have to study the Cognitive Functions of MBTI, which is a little more advanced than the basic overview and quick online quiz that was linked in the earlier posts. There are eight cognitive functions: Introverted Sensing, Extraverted Sensing, Introverted Intuition, Extraverted Intuition, Introverted Thinking, Extraverted Thinking, Introverted Feeling, and Extraverted Feeling. Basically, each person uses two Extraverted Functions and two Introverted functions, which shape their personality. Once you identify those and which ones you use the most, it is a much more accurate way of determining your personality type. This may be a little to in depth for an introduction to MBTI, but If you're interested in figuring out more about your type blondguy, I would suggest reading online about these Cognitive Functions. Here's the most accurate test for MBTI I have ever taken and it uses the Cognitive Functions:
http://www.cognitiveprocesses.com/asses ... p_old.html