M u d r â s

Buddhas and Bodisattvas and frequently other deities are shown with their hands forming a number of different ritualized and stylized poses (Mudrâs). They may be holding different objects as well within these poses. Each by itself and in combination with others have specific meanings. Some of the more common ones are depicted below.

Right-Hand Gestures
"Gesture of Protection" (abhaya) This gesture is also called "Gesture of Fearlessness" or "blessing" or "fearless mudra". Generally, this position is shown with the palms(s) facing outward and the fingers extended upwards. The arm is elevated and slightly bent. You can find abhayamudrâ sometimes also as a left-hand gesture. This mudra is characteristic of Buddha Shakyamuni and Dhyani Buddha Amogasiddhi.
"Gesture of Argument" (vitarka) Also called "The Gesture of Debate" or "discussion" mudra. In this gesture the tips of thumb and index finger touched forming a circle. All the other fingers are extended upwards. This is the mystic gesture of Taras and Bodhisattvas, often used when explaining the Buddha�s teachings.
"Gesture of Witness" (bhumisparsha) This gesture is also called "touching the earth" mudra or "calling the earth to witness" mudra. The right arm hangs down over the right knee. The hand with the palm turned inward and all the fingers extended downward with the finger touching the lotus throne. The left hand lies on the lap with palm upward. This gesture symbolizes Shakyamunis victory over Mara. The Dhyani Buddha Akshobhya shows the same Mudra.
"Gesture of Charity" (varada) This gesture is also called "Gift bestowing Gesture of Compassion" or "conferring boon" or "grace" mudra. The arm is extended all way down with palm facing outwards. You can find varadamudrâ sometimes also as a left-hand gesture. This is the mudra of Dhyani Buddha Ratnasamhava, Bodhisattva Avalokiteshvara and (sometimes) standing Buddha Shakyamuni.
"Gesture of ascetic" (shramanamudrâ) This gesture is also called renunciation mudra. The hand points downward away from the body as a symbol for renunciation of secular pleasures.
"Gesture of Understanding" (cincihna) In this mudra, the thumb and index finger grasp a fine object as a a grain of truth. This is a symbol for spiritual understanding.
"Gesture of Threatning" (tarjana) This gesture is also called "warning" mudra. Only the index finger is raised either horizontally or vertically, while the other fingers are locked up in the fist. You can find abhayamudrâ sometimes also as a left-hand gesture. This mudra is characteristic of most of the wrathful deities.
"Gesture of Banishing" (karana) also called the "The Gesture Warding off Evil", this mudra indicates with the hand stretched out, either horizontally or vertically, palm turned forward. The thumb presses down the middle two fingers (like the horns of a Yak against an enemy), while the index and little fingers extend straight upwards. You can find abhayamudrâ sometimes also as a left-hand gesture. Ekajata and Yama, as well as Vajrapani and Bhutadamaravajrapani are frequently shown in this mudra.
"Gesture Beyond Misery " (Buddhashramana) Also called the ascetic�s Gesture of Renunciation.. In this mudra the right hand is lifted in line with the shoulder, the wrist bends backwards and the fingers and the palm face upwards. The fingers point outward, away from the body. The is the gesture of Vasudhara and Usnishijaya.
"The Performance of Homage Gesture" (tarpana) The arms are bent at the elbow with hands raised even with shoulders. The fingers are slightly bent with the fingertips extending toward the shoulders. The palms of the hands face downwards. A mudra frequently used by Namasangiti.
"The Lion Gesture" (harina) In this mudra the thumb along with the second and third fingers touch the tips, forming a ring. The little and the index fingers extend upwards. Frequently, symbols or emblems are held in this manner. Also denotes rabbit or hare, or elephant.
"Gesture of Knowledge" (Jnana) The tips of the index finger and the thumb join, forming a circle, the other fingers are extended straight. This mudra is held against the chest, palm towards the chest. In this way, it differs from the vitarka mudra in which the palm faces away from the body.
"Gesture of Discord" (kartari) This mudra is held with the hands at shoulder level. The thumb and the ring finger (third finger) touch the tips forming a circle. The index and middle finger extend straight resembling rabbits ears or the horns of a deer. Frequently, symbols appear between these two fingers.
Left-Hand Gestures
"Gesture of leisure" (avakasha) The sitting person is holding the left hand on his/her lap, palm upwards.
"Flower-holding Gesture" (kataka) A fist-like mudra in which the fingers bend together until the thumb and the index finger meet, forming an open tube. This position is frequently used in icons in which fresh flowers or other venerated objects are inserted.
Both hands Gestures
"Gesture of Meditation" (dhyana) It is also called Samadhi or Yoga Mudra. Both hands are placed on the lap, right hand on left with fingers fully stretched and the palms facing upwards. This is the characteristic gesture of Buddha Shakyamuni, Dhyani Buddha Amitaba and the Medicine Buddhas.
"Gesture of Meditation with bowl" The Gesture of Meditation is also shown with a begging bowl, but not with any other kind of bowl.
"Gesture of Teaching" (dharmacakrapravartana) In this gesture both hands are held against the chest, the left facing inward, covering the right facing outward. The index finger and the thumb of each hand making a circle. It is characteristic of Dhyani Buddha Vairocana. It is also a gesture of hands exhibited by Lord Buddha while preaching the first sermon in Sarnath.
"The Embracing Gesture" (vajrahûmkara) also called "The Om Sound Gesture". The wrists are crossed at the breast. The hands hold the Vajra (=thunderbolt, male) and Ghanta (= bell, female). The right hand crosses over the left at the wrist, palms facing inwards towards the chest and usually over the heart, symbolizing the union of method and wisdom. This is the gesture of Adi Buddha Vajradara, Samvara and Trailokyavijaya.

"Gesture of Knowledge Fist" (vajramudra) The right hand makes a fist, thumb enclosed, index finger extended upward, palm out; the left hand forms a fist, palm inward and encloses the extended index finger. You will find this gesture very often mirror-inverted.

"Gesture of Perfection" (uttarabodhi) This gesture is also called "best-perfection" mudra. In this position all fingers are intertwined. The index fingers extend straight up and are together. Frequently, Shakyamuni Buddha as liberator of the Nagas presents this mudra
"Gesture of Nectar Sprinkling" (kshepana) Also called "Sprinkling of Ambrosia" mudra. The two hands join, palm to palm, and the index fingers extend together and usually point downwards toward a vase or container. The other fingers and the thumbs are interwined.
"Gesture of Praying" (namaskara or anjali) Also called the simple namaste (prayer) position (means "I bow to you.") In this gesture, the hands are kept close to the chest in devotional attitude with the palms and fingers joined. This is the special gesture of Avalokiteshvara with more than two arms.
"Gesture of Holding the Jewel" (manidhara) The hands are arched and hold a wishing jewel, which can not be seen because of its transparency. This is a mudra of Avalokiteshvara, and is often confused with the similar gesture of greeting.

"Warding Off Evil Gesture" (Bhûtadâmara) Also called "Trailokyavijaya" or awe-inspiring mudra. It shows the hands crossed at the wrist, the right hand over the left hand, palms turned outwards. Usually the two middle fingers are slightly bent and the hands may both hold additional symbols like Vajras and Ghanta. This gesture is frequently seen in the representations of Vajrapani and Bhutadamaravajrapani

Here with illustrations: http://www.buddhas-online.com/mudras.html