The Endless Forest is a COMPLETELY FREE multiplayer online game and social screensaver, a virtual place where you can play with your friends. When your computer goes to sleep you appear as a deer in this magical place. There are no goals to achieve or rules to follow. Just run through the forest and see what happens.

Here is a snippit from the website itself:

You are a deer. So are the other players. You meet each other in an endless forest on the internet. The setting is idyllic, the atmosphere peaceful. You communicate with one another through sounds and body language.
Currently The Endless Forest consists of a forest, a mysterious ruin, a lovely pond and as many deer as there are players at any given time. You can play the game anonymously but we encourage you to name your deer so other players can recognize you.

Although not goal-oriented, there are several activities that you can engage in. Nothing very demanding or violent. Just fun things to do in a nice environment.
Once every so often, the forest deities will appear, either in person or through their divine powers. Beware of falling rocks and sudden showers!

The Endless Forest is a magnificent piece of social artwork for all ages. Sounds interesting to you? Click here to start your adventure!