You can be a missionary without even leaving your armchair! The Virtual world is a rapidly expanding mission field. Here are a few organisations and sites who work in this area:
ChatnowChatnow is an international organisation whose aim is to provide those in need with the opportinity to chat online with a spiritual coach 24 hours a day, 7 days a week. We aim to provide spiritual advice based on the teachings of the Bible. They are looking for volunteers to help with spiritual coaching.
YesHEisThe purpose of yesHEis.com is to help you share Jesus online. By gathering the Internet's best Christian evangelistic media, they are building a resource base to help you share Jesus to almost any type of person, in any situation.