I find books (and the Internet) an important resource in developing my understanding of personality type.
The books below are some of those I have personally found helpful. (These links all work as of Aug 2011)
Gifts Differing: Understanding Personality Type - The original book by Isabel Briggs Myers who developed the MBTI. Clear and readable, focusing mainly on the strengths of each Personality Type. Also describes how the system was developed.
What Type am I? - A really clear and simple explanation of the basics of type. Well laid out with cartoons and bullet points, making it easy to dip into. A recommended 'first' book, especially if you don't like the idea of masses of dense text.
Type Talk - A lively and observant look at the different Personality Types, and how to see the differences in people around you. Includes more of the weaknesses of each type, rather than just the strengths. Also uses Temperament as a way of grouping types for ease of recognition.
Do What You Are - A great book to investigate possible career choices in relation to Personality Type, with worksheets to help you think through your own situation.
Nurture by Nature - Applying the understanding of Personality Type to parenting. A fascinating look at how Type develops through maturity, and very practical.
Just your Type - Understanding the joys and stresses of couple relationships between the different Personality Types.
Was that really me? - Sometimes when we're under particular pressure, we find ourselves behaving differently, or 'out of character'. This book looks at how these behaviours may be linked to our basic Personality Type, and are an expression of of our 3rd and 4th functions. It is a deeper look into the dynamics of Type.
Personality Type: An Owner's Manual - Read this book if you want to get a thorough understanding of Type dynamics and the Jungian functions, and how they relate to each of the 16 MBTI Personality Types. Very clear descriptions of what it all means, but not light-weight.
Survival Games Personalities Play - An advanced book for practitioners and clinicians, looking at the 4 temperaments, their core needs, what might trigger them to become dysfunctional, and how that is evidenced. Intervention strategies for clinicians included.
Pray Your Way - An interesting look at how differences in Personality Type preferences lead to different approaches to prayer and spirituality. Logical, when you think about it.
Soul Types - This book offers a deeper understanding of Personality Type and type dynamics, in the context of what supports or hinders our spiritual development. Very clear, grouped by dominant function and laid out in a way that makes it easy to compare between types. The recent edition has been re-written - my experience is of the older one.
I have personally found the links below helpful in my coaching. Remember that free questionnaires are not as reliable as those backed by research. Don't take the results at face value in either case, but always explore further to decide which type you think fits you best. (Links all work as of Aug 2011)
Free personality type quiz - from HumanMetrics. Includes additional links to career information and relationships.
Free type quiz and descriptions - Team Technology have developed some good descriptions and a number of free reports. Try taking it a few times, see if your results differ and if you can find the type that fits best.
Personality type & career - A good, thoughtful quiz by author Paul Tieger, allowing considered self-assessment with understanding. It has recently been re-worked, and now includes an optional paid-for career report.
The sixteen Myers-Briggs types - Some really excellent longer descriptions (up to about four pages) of each of the types. Draws out more of the subtle differences between whole types, to help you decide between them.
Jungian function theory - This is the basis of the M-B system, and gives a clearer idea of the dynamics involved in the inter-relationship between preferences. The 'working out the letters' approach is really just a shortcut for getting at the underlying dynamics discussed here. A good, clear description.
Working out your team role - A look at one's role at work and a comparison with psychological type, providing a possible basis for understanding the stress points and potential directions for change or challenge in your job.
MBTI Complete is an American site which gives you the MBTI questionnaire online and then leads you through a self-analysis to help you find your best-fit type. The site is supportive and informative, costs $60 and may be a good back-up option.
British Association of Psychological Type - a UK organisation supporting people interested in psychological type, whether practitioners or not. They have an annual conference and a quarterly journal.