I've always found various astrology systems to be interesting. I am especially a fan of Celtic Tree astrology. I am the Elder Tree in Celtic Tree Astrology (because of my late December birthday).
Here is a list of the signs so you can find yours as well.
Birch - The Achiever (December 24 - January 20): If you were born under the energy of the Birch you can be highly driven, and often motivate others they become easily caught in your zeal, drive and ambition. You are always reaching for more, seeking better horizons and obtaining higher aspirations. The Druids attributed this to your time of birth, which is a time of year shrouded by darkness, so consequently you are always stretching out to find the light. Birch signs (just like the tree) are tolerant, tough, and resilient. You are cool-headed and are natural-born rulers, often taking command when a situation calls for leadership. When in touch with your softer side, you also bring beauty in otherwise barren spaces, brightening up a room with you guile, and charming crowds with you quick wit.
Rowan - Thinker (January 21 - February 17): Celtic tree astrology recognizes Rowan signs as the philosophical minds within the zodiac. If you were born under the Rowan energy, you are likely a keen-minded visionary, with high ideals. Your thoughts are original and creative, so much so, that other's often misunderstand from where you are coming. This sometimes makes you aloof when interacting with others as you feel they wouldn't understand where you are coming from anyway. Nevertheless, although you may appear to have a cool exterior, you are burning within from your passionate ideals. This inner passion provides inner motivation for you as you make your way through life. You have a natural ability to transform situations and people around you by your mere presence. You are highly influential in a quiet way and others look to you for your unique perspectives.
Ash - The Enchanter (February 18 - March 17): Those born under the Celtic tree astrology sign of the Ash are free thinkers. Imaginative, intuitive, and naturally artistic, you see the world in water-color purity. You have a tendency to moody and withdrawn at times, but that's only because your inner landscape is in constant motion. You are in touch with your muse, and you are easily inspired by nature. Likewise, you inspire all that you associate with and people seek you out for your enchanting personality. Art, writing (especially poetry), science, and theology (spiritual matters) are areas that strongly interest you. Others may think you are reclusive, but in all honesty, you are simply immersed in your own world of fantastic vision and design. You are in a constant state of self-renewal and you rarely place a value on what others think about you.
Alder - The Trailblazer (March 18 - April 14): If you are an Alder sign within the Celtic tree astrology system, you are a natural-born pathfinder. You're a mover and a shaker, and will blaze a trail with fiery passion often gaining loyal followers to your cause. You are charming, gregarious and mingle easily with a broad mix of personalities. In other words, Alder signs get along with everybody and everybody loves to hang around with you. This might be because Alder's are easily confident and have a strong self-faith. This self-assurances is infectious and other people recognize this quality in you instantly. Alder Celtic tree astrology signs are very focused and dislike waste. Consequently, they can see through superficialities and will not tolerate fluff. Alder people place high value on their time, and feel that wasting time is insufferable. They are motivated by action and results.
Willow - The Observer (April 15 - May 12): If you are a Willow sign, you are ruled by the moon, and so your personality holds hands with many of the mystical aspects of the lunar realm. This means you are highly creative, intuitive (highly psychic people are born under the sign of the Willow) and intelligent. You have a keen understanding of cycles, and you inherently know that every situation has a season. This gives you a realistic perspective of things, and also causes you to be more patient than most tree signs. With your intelligence comes a natural ability to retain knowledge and you often impress your company with the ability to expound on subjects from memory. Willow Celtic tree astrology signs are bursting with potential, but have a tendency to hold themselves back for fear of appearing flamboyant or overindulgent. It is your powers of perception that ultimately allow your true nature to shine, and what leads you to success in life.
Hawthorn - The Illusionist (May 13 - June 9): Hawthorn signs in Celtic tree astrology are not at all what they appear to be. Outwardly, they appear to be a certain persona, while on the inside Hawthorn's are quite different. They put the term "never judge a book by its cover" to the test. They live seemingly average lives while on the inside they carry fiery passions and inexhaustible creative flame. They are well adjusted and can adapt to most life situations well - making themselves content and comforting others at the same time. You are naturally curious, and have an interest in a broad range of topics. You are an excellent listener, and people seek you out as an outlet to release their burdens. You have a healthy sense of humor, and have a clear understanding of irony. You tend to see the big picture, and have amazing insight - although you typically won't give yourself enough credit for your observations.