There are 3 Types of Symbiotic Relationships

Mutualism: When both organisms benefit in the relationhip.

Commensalism: When one organism benefits while the other remains neutral.

Parasitism: When one organism lives off the other and gains all the benefits and the host is hurt.

The link below talks about the three differenty types of symbiosis:
Link: http://www.squidoo.com/natures-fascinating-symbiosis

Brainpop Video:
Video: http://www.brainpop.com/science/livingsystems/symbiosis/preview.weml

Watch the video below for a variey of symbioic relationships (10 minutes)
Video: http://www.neok12.com/php/watch.php?v=zX47406078527e6f4c77685d&t=Ecosystems