Some common asanas

Asana (Sanskrit, to sit down) is a body position, associated with the practice of Yoga. These are widely known as Yoga postures or Yoga positions.

A few useful links that illustrate some of the more popular asanas are posted below:

Yoga Circle

Asanas

Yoga Postures Step-By-Step

References:
Asana. Wikipedia.
Image source: Dhanurasana, Bow. Wikipedia, GNU Free Documentation License.