What are Mundras?

"n Buddhist sculpture and painting throughout Asia, the Buddha (Nyorai, Tathagata) are generally depicted with a characteristic hand gesture known as a mudra. Mudras are used primarily to indicate the nature and function of the deity. They are also used routinely by current-day Japanese monks in their spiritual exercises and worship. Knowledge of these hand gestures can help greatly in identifying Buddha images (less so when trying to identify Bodhisattva / Bosatsu images). But there is much variation and overlap among the mudra, and traditions in Japan differ from those in mainland Asia, so one should not depend exclusively on mudra for identification.

The most widely known mudra in Japan are those associated with the Five Buddha of Wisdom (Jp = Godai Nyorai, Gochi Nyorai), a grouping that originated in India, as did most Buddhist iconography. The five are eminations of Buddha nature. They embody five fundamental wisdoms -- wisdom against anger, envy, desire, ignorance, and pride -- to help us break free from the cycle of death and rebirth (samsara). Each of the five has a specific mudra that corresponds to one of the five defining episodes in the life of the Historical Buddha (see charts below). Each of the five is also associated with a compass direction, color, and other attributes. In Japan, only two of the Five Buddha are still widely reverred. 
The five are:
Teaching Mudra, Dainichi Nyorai (Vairocana) | Center | White | Well known in Japan.
Fear Not Mudra, Fukūjōju Nyorai (Amoghasiddhi) | North | Green
Welcome Mudra, Hōshō Nyorai (Ratnasambhava) | South | Yellow
Earth-Touching Mudra, Ashuku Nyorai (Akshobhya) | East | Blue
Meditation Mudra, Amida Nyorai (Amitabha) | West | Red | Well known in Japan."
See other well-known mudra are also presented [on Onmarkproductions]

More Info...

1. Mundras @ 3Ho
2. Mundras picture gallery @ about (dot) com
3. The Healing Practice of Mudras
4. Mudras for Benefits
5. Introduction to Mudras @ Eclectric Energies