What present should I offer to my Aries female friend on her b-day?

Since she's an Aries, don't give her a gift that is too practical or organizational -- the gift that challenges her, starts a new project/hobby, or utilizes some of their intense physical energy will be loved the most. Some suggestions include disposable or Polaroid camera, how-to video or book for a new hobby, a book on tape, or a puzzle.

The Forer effect is the observation that individuals who will give high accuracy ratings to descriptions of their personality that supposedly are tailored specifically for them. They are, in fact, vague and general enough to apply to a wide range of people. This effect can provide a partial explanation for the widespread acceptance of some beliefs and practices, such as astrology, fortune telling, and types of personality tests. A related and more general phenomenon is that of subjective validation. The horoscope section in Yahoo Answers is a perfect example of this behavior.

Subjective validation occurs when two or more unrelated or even random events are perceived to be related because a belief, expectancy, or hypothesis demands a relationship. Thus people seek a correspondence between their perception of their personality and the contents of a horoscope. You have a great need for other people to like and admire you. You have a tendency to be critical of yourself. You have a great deal of unused capacity which you have not turned to your advantage. While you have some personality weaknesses, you are generally able to compensate for them. Disciplined and self-controlled outside, you tend to be worrisome and insecure inside. At times you have serious doubts as to whether you have made the right decision or done the right thing. You prefer a certain amount of change and variety and become dissatisfied when hemmed in by restrictions and limitations. You pride yourself as an independent thinker and do not accept others' statements without satisfactory proof. You have found it unwise to be too frank in revealing yourself to others. At times you are extroverted, affable, and sociable, while at other times you are introverted, wary, reserved. Some of your aspirations tend to be pretty unrealistic. Security is one of your major goals in life.

Money to let her decide on whats a good gift for herself! Thats the best!