Sorry to bring that out on the table again, but i've been really interested lately by the Myers-Briggs Type Indicator which is not used to define who you are and your motivations, but how your personality interact with the world.
I was very skeptical at first but then I've tried the test on several people i know well IRL (friends, family etc 14 persons to be accurate), and i can tell you that stuff is really really accurate to define a general behavior.
Consider the general descriptions of a type to be at the center of each case and each person of a same type varying around that point.
[Blocked Image: http://www.harding.edu/career/images/MBTI1.gif]
With 4 variables varying from each extreme.
E/I : The first one was (E)xtroversion vs. (I)ntroversion. This stands how people prefer to focus their attention(interest) and get/spend energy. In the extraverted attitude the energy flow is outward, and the preferred focus is on people and things, whereas in the introverted attitude the energy flow is inward, and the preferred focus is on inner thoughts and ideas.
S/N : sensing, intuition : (S)ensing vs. i(N)tuition. Sensing and Intuition are the perceiving functions. They indicate how a person prefers to receive data from the environment around him. These are the nonrational functions, as a person does not necessarily have control over receiving data, but only how to process it once they have it. Sensing prefers to receive data primarily from the five senses(sight, hearing, taste, smell, touch), and intuition prefers to receive data from the unconscious, or seeing relationships via insights. Often it is called "sixth sense" or "gut feel".
T/F : thinking, feeling : Thinking and Feeling are the rational functions. They are used to make rational decisions concerning the data they received from their perceiving functions, above. Thinking is characterized as preferring to being logical, analytical and thinking in terms of "true or false". Thinking decisions tend to be based on more objective criteria and facts. Feeling, which refers to subjective criteria and values, strives for harmonious relationships and considers the implications for people. Feeling decisions tend to be based on what seems "more good or less bad" according to values.
J/P : judging, perception : And the 4th scale even it could be met in the Jungian works was truly added by Myers-Briggs team. (J)udging vs. (P)erceiving. It shows how people relate to the world around them. The J person tends to prefer to create and live in an ordered environment. Words like "structured" and "controlled" come to mind. Js tend to "plan their work and work their plan." They often come across as "decisive". The P individual tends to prefer a flexible, wait-and-see environment. Words like "spontaneous" and "adaptable" and "open-minded" best describe him or her.
And here's the test for those who didn't do it. Or those who maybe have made it in a rush.
http://www.humanmetrics.com/cgi-win/JTypes2.asp
Description of each type http://www.e-mbti.com/ (there is also much more on the net if you look for it yourself)
Personally i'm INFP ( The Healer ) spot-on :
INFPs are quiet, creative, sensitive and perceptive souls who often strike others as shy, reserved and cool. These folks have a rare capacity for deep caring and commitment--both to the people and causes they idealize. INFPs guide their behavior by a strong inner sense of values, rather than by conventional logic and reason. Forced to cope with this facts-and-figures "real" world we inhabit, INFPs may appear to have been imported from another galaxy! They gravitate toward creative or human service careers which allow them to use their instinctive sens of empathy and remarkable communication skills. Strongly religious, spiritual or philosophical people, INFPs may see the purpose of their lives as an inner journey, quest or personal unfolding. More practical or rational types may tend to discredit the INFP's sources of understanding as mystical. The search for a soulmate is a preoccupation for many INFPs, who must balance their need for privacy and peace with their yearning for human connection. If there seems to be an air of sadness in the INFP's spirit, blame it on this type's longing for the perfect in all things.
As an INFP, your primary mode of living is focused internally, where you deal with things according to how you feel about them, or how they fit into your personal value system. Your secondary mode is external, where you take things in primarily via your intuition.
INFPs, more than other iNtuitive Feeling types, are focused on making the world a better place for people. Their primary goal is to find out their meaning in life. What is their purpose? How can they best serve humanity in their lives? They are idealists and perfectionists, who drive themselves hard in their quest for achieving the goals they have identified for themselves
INFPs are highly intuitive about people. They rely heavily on their intuitions to guide them, and use their discoveries to constantly search for value in life. They are on a continuous mission to find the truth and meaning underlying things. Every encounter and every piece of knowledge gained gets sifted through the INFP's value system, and is evaluated to see if it has any potential to help the INFP define or refine their own path in life. The goal at the end of the path is always the same - the INFP is driven to help people and make the world a better place.
Generally thoughtful and considerate, INFPs are good listeners and put people at ease. Although they may be reserved in expressing emotion, they have a very deep well of caring and are genuinely interested in understanding people. This sincerity is sensed by others, making the INFP a valued friend and confidante. An INFP can be quite warm with people he or she knows well.
INFPs do not like conflict, and go to great lengths to avoid it. If they must face it, they will always approach it from the perspective of their feelings. In conflict situations, INFPs place little importance on who is right and who is wrong. They focus on the way that the conflict makes them feel, and indeed don't really care whether or not they're right. They don't want to feel badly. This trait sometimes makes them appear irrational and illogical in conflict situations. On the other hand, INFPs make very good mediators, and are typically good at solving other people's conflicts, because they intuitively understand people's perspectives and feelings, and genuinely want to help them.
INFPs are flexible and laid-back, until one of their values is violated. In the face of their value system being threatened, INFPs can become aggressive defenders, fighting passionately for their cause. When an INFP has adopted a project or job which they're interested in, it usually becomes a "cause" for them. Although they are not detail-oriented individuals, they will cover every possible detail with determination and vigor when working for their "cause".
When it comes to the mundane details of life maintenance, INFPs are typically completely unaware of such things. They might go for long periods without noticing a stain on the carpet, but carefully and meticulously brush a speck of dust off of their project booklet.
INFPs do not like to deal with hard facts and logic. Their focus on their feelings and the Human Condition makes it difficult for them to deal with impersonal judgment. They don't understand or believe in the validity of impersonal judgment, which makes them naturally rather ineffective at using it. Most INFPs will avoid impersonal analysis, although some have developed this ability and are able to be quite logical. Under stress, it's not uncommon for INFPs to mis-use hard logic in the heat of anger, throwing out fact after (often inaccurate) fact in an emotional outburst.
INFPs have very high standards and are perfectionists. Consequently, they are usually hard on themselves, and don't give themselves enough credit. INFPs may have problems working on a project in a group, because their standards are likely to be higher than other members' of the group. In group situations, they may have a "control" problem. The INFP needs to work on balancing their high ideals with the requirements of every day living. Without resolving this conflict, they will never be happy with themselves, and they may become confused and paralyzed about what to do with their lives.
INFPs are usually talented writers. They may be awkard and uncomfortable with expressing themselves verbally, but have a wonderful ability to define and express what they're feeling on paper. INFPs also appear frequently in social service professions, such as counselling or teaching. They are at their best in situations where they're working towards the public good, and in which they don't need to use hard logic.
INFPs who function in their well-developed sides can accomplish great and wonderful things, which they will rarely give themselves credit for. Some of the great, humanistic catalysts in the world have been INFPs.
Now i understand why i often come off as weird for some people ;x
also :
An interesting table defining the relations between each type http://www.socionics.com/rel/relcht.htm, i've already experienced practical tests of that 
It also has already been discussed on 2 threads
