I am a graduating chiropractic student. As a doctor, how do I sign up
with insurance companies? Is there a listing of all insurance
companies (HMO's, PPO's....) with links to their websites?

Good question.  HMO and PPO change so frequently that a site would not
be accurate should it exist.  Suggestion, call the other pratitioners
in the area you plan to practice and tell them you are scouting new
insurance and you want to be sure that their service is covered.  They
will tell you who they accept.  Then contact them as a prospective new
provider.  Doesnt your school have a business course that teaches
business administration?  Were you sleeping through that part?
Dr. T

Thanks Dr. T, yes we did learn that in business class. As with any
school, the teachers have not been the field for awhile, and they can
run a little behind the real world. I was looking for a site that
would also give some details about their plans. Just figured that
someone would have found a way to make some money off a website that
listed insurance providers by state and local regions by now.