LambdaMOO

LambdaMOO is an online community of the variety called a MOO. It is the oldest MOO today.

LambdaMOO was founded in late 1990 or early 1991 by Pavel Curtis at Xerox PARC. Now hosted in the state of Washington, it is operated and administered entirely on a volunteer basis. Guests are allowed, and membership is free to anyone with an e-mail address.