Electronic Pen Pals: messages are exchanged with peers in another school, state, or country.  Consider cross-cultural or cross-age pairings or groups.  May be done at individual or group levels.

Peer-to-Peer Tutoring (aka electronic mentoring): links students  with others who provide one-on-one assistance and guidance on a routine basis.  May use email or chat.

Round-Robin Publishing:  a class or group starts a story with one paragraph and sends it to another class.  Students work to add a new paragraph to the story, and the story variations rotate to the next class.

HTML Publishing:  this may be as simple as a student homepage created by typing in a form, or as elaborate as creating entire web sites.