Hi, there, Connie!
Disney buses do run from Park to Park as well as from Parks to Resorts. They do not run between Resorts; you would have to transfer at a Park if you were going, say, from Disney's Animal Kingdom Lodge to Disney's Beach Club.
There is no direct route between any two resorts via bus; the exception to this rule is any group of Resorts that share a bus (the All-Stars, for example).
Per the
official Web site, your only listed option is to take a bus. Of course, taxis are readily available at every Park, and that is certainly something to consider if time is a concern.
Thanks for checking in; please let me know if I can be of any further assistance!
See you later, celebrator,
-Deborah B.