Agar-agar is a tasteless, dried seaweed derivative that acts as a setting agent like gelatin. However, unlike the animal-derived gelatin, it is a vegetarian substitute. Rich in protein and minerals, agar-agar, also called kanten, becomes gelatinous when dissolved in water, heated, and then cooled. It can even set in room temperature, unlike gelatin.

Agar-agar is widely used in Asia to make desserts and other dishes. You can find it in Asian grocery stores or natural food stores, and they come in blocks, powder or strands.

References:

http://www.foodsubs.com/ThickenGelatins.html

http://www.foodterms.com/encyclopedia/agar/index.html