I'm a Certified Myers-Briggs Practitioner (and an INFJ), so I have to just mention that the online "tests" and such are not the best way to find out your type. In my training, I learned that even the actual MBTI instrument is only 70% accurate.
The best way to find your "best fit type" is to meet one-on-one with a practitioner who will help you self-select your type, then give you the instrument (that's what they call the authentic MBTI), compare the results, and work with you until you can harmonize them (we're trained in different strategies for that).
Also, if you get deeper into the MBTI, that's where it becomes the most useful. Each letter (preference) actually represents a different "function" which is introverted and extraverted. We all have 8 functions, which we use in a different order. The first four are our conscious functions and the next four are subconscious.
For example, as an INFJ, I operate like this:
Dominant function: introverted intuition (how I internally do stuff)
Auxilary function: extraverted feeling (how I relate to others)
Tertiary function: introverted thinking (my "hobby" function - in this case, analyzing)
Inferior function: extraverted sensing (my least developed of my conscious functions - in this case, "hands-on" stuff)
...and that's all for today's lesson in personality typing! I can't help myself because I've been giving seminars off and on since college, and used to blog about this often. I have a shelf of books - some incorporating Christianity - and a collection of the best website resources. Blame it on my INFJness! We're a little odd, being the rarest type (less than 1% of the population).
Seriously, though, if anyone is interested in a consultation, it can be done long distance - I charge the same price as the online option ($60 plus any long distance phone charges, if needed), but you'll get a real person taking you through the dynamic process instead of a static impersonal report.
(I'm planning to post my previous writings on this subject to the archives soon)