Symbols (As excerpted from pacific.net:80)

Throughout time, symbolism and meaning have been ascribed to geometric form, numbers, and other expressions of the dynamic aspect of our spiritual energies. The forms which reflect "divine nature" have been used over time until now, as we rediscover their meanings and uses, we continue their expression anew. Symbols carry these dynamic archetypal qualities and often have multiple layers of meaning. We urge you to discover for yourself, through your own experience, the many such possible meanings of the symbols you choose to use in your own spiritual search and rituals. And, in order to offer some guidance, we offer the following bits of information, gleaned from numerous resources and from our own personal experience... Magical Stars and Interlaced Patterns
There has long been interest in the talismanic value of different numbers and their varied many-pointed stars or patterns. This collection is a result of our own interest and desire to bring you the beauty and magic of the sacred geometric forms long in use from the Far East and India, from the Middle East, Greece and the Celtic lands, through time and the uses of Alchemists, Magicians, Caballists, and now You. Many of these designs are of an interlaced single line - considered to be spiritually protective as it is a continuous enclosure, unbroken and therefore "gateless" - thus no evil or undesired energy can enter into the circle of the pattern, it is a complete and endless cycle unto itself. Magical circles are often drawn in this same way, to create a space "between the worlds" - a safe place for the work at hand to be done. We offer you here not only the radiant symmetry and power of the pentagram, but also its many related and powerful friends of different multipointed facets and archetypal meanings... The Pentagram
In ancient times, the pentacle was revered as a symbol of life - the four classical elements of earth, air, fire and water, join with spirit to create life. Wearing the pentagram was and is viewed as protection and as a talisman of divine life and good health. Did you ever notice that the natural way to draw a "star" is by making a pentagram, or that cutting an apple crosswise reveals the Earth Mother's own pentagram? Since the apple has been a sacred symbol of knowledge and eternal life for thousands of years in many different cultures, this certainly gives the geometric pentagram almost "genetic" weight as an unconscious universal symbol of life! The protection of the pentagram can be invoked by using the pentagram to make the "sign of the cross": beginning at the left breast, with the right hand, go to the forehead, to the right breast, then left shoulder, right shoulder and end at the left breast. A cycle is complete, the end is the beginning. This continuous and closed or gateless sign of protection was used long before the Christians began to cross themselves with a four-pointed cross. The numerical properties of the pentagram also includes its 13 sides (13 lunar months), and its 8 points for the 8 seasonal rituals. Double Pentagram
This pentagram has often represented the Goddess in her five stages of a woman's life: birth, menarche, maternity, menopause and death, her interlaced, interwoven "arms" representing heaven and earth together. Ringed Pentagram
The interlacing of points and circles, a pentagram with five rings was considered very mystical and harmonious, male and female weaving endlessly and blending together in perfect balance. The Hexagram
Solomon's Seal Long before this hexagram became the emblem of Judaism, it was revered as the symbol of the joining of opposites - spirit and matter, yin to yang, heaven to earth, Shiva and Kali - that maintains life in the cycles of creation and destruction. The Seal of Solomon is a seal of protection and contains the invisible Seventh Seal made from the four elements plus the divine number 3. This symbol also was used in alchemy to symbolize alcohol - (fire and water), a union of water and heat in perfect harmony. This possibly derived from the Hindu union of male-fire-lightning with female-water-ocean in the heart chakra (Anahola). In fact, the connection to the male-female union carries over also in the "Sri Yantra" symbol of many triangles intersecting heaven and earth. GREEK: (Pythagorean system) Aphrodite (Goddess of Love) - the union of 2 and 3 METAPHYSICS: The symbol of the Order of the Golden Dawn The Magic Hexagram
This "gateless" version of the hexagram was designed by Aleister Crowley as a symbol of his Order of the Silver Star (Astrum Argentum) because of their need in ritual for the protection that an unbroken or gateless pattern would provide- no evil spirit or undesired energy can enter where there is no "lifting" of the knife or pen as the pattern is drawn. The number 6 on the Tree of Life signifies the Sun - the fusion of spirit with matter in balance, giving great energy - very positive and decisive, radiating from the center outward with exuberance and joy. It is the "heart chakra" of the tree and the symbol of the resurrected God. Six is a "perfect number", as 1 + 2 + 3 = 6. End of Excerpt
Also, I would like to mention the knotted circle as seen in symbolism.
The circle is a continous strand of life, a cycle of death and rebirth, as seen in the theory of reincarnation.