The Mages Guild maintain a network of teleporters, the Guild Guides, adept mystics who can teleport other persons instantaneously to a well-known location. Guides in guildhalls offer their services to anyone who can afford them.
Most guild guides on the Mainland will only teleport you to guild halls under the jurisdiction of the same archmage. Some guild halls have a second guild guide however (currently Firewatch, Vivec and Old Ebonheart) that can teleport you further afield.