From Chapter 11 of the Big Red Book of ACA, page 365-390:
Fellow Traveler – This is a traditional method of ACA sponsorship. A person is willing to share experience, strength, and hope in helping the sponsee work his or her way through the Twelve Steps and to pick up the recovery tools for facing life on life’s terms.
Temporary Sponsor – Serves as an interim sponsor for a short time until a permanent one is found.
Multiple Sponsors – More than one sponsor to serve various needs of the sponsee, as long as the sponsee isn’t hiding out in the various relationships. We don’t use multiple sponsors to avoid intimacy with one person or to “shop” for an opinion that we desire.
Co-Sponsors – Where two people are in agreement to sponsor each other. This model seems to work best for ACA members having significant time and experience in the program.
Long Distance Sponsors – This can work well for geographically isolated ACA members. There is snail mail, e-mail, telephone, tape recordings, and voice stream where distance or circumstances prevent person-to-person contact. Additionally, the Internet has made these long distance relationships more meaningful.
Some ACA members who are geographically isolated use online ACA meetings, ACA teleconference [phone bridge line] meetings, and live chat to work an ACA program. They use a private chat room or the telephone to do extensive Step work with a long distance sponsor. In addition to the Steps, there can also be discussion and meaning found in the Twelve Traditions in this method of sponsorship.
ACA Arizona has a great page on their website regarding sponsorship. Check it out here.