Just as patients need to know their options when deciding about a given type of medical intervention - informed consent - you also need to know about your options in deciding on a medical specialty.
Check these sources for information about specialties:
University of Kansas School of Medicine Specialty Choice Guide
Careers in Medicine
AOA Specialty Affiliates
Washington University School of Medicine's Guide to Specialties
Osteopathic Specialty Residency Requirements; AOA Postdoctoral Training
Subspecialty Categories