Special Area Codes:

700 assigned to interexchange carriers for their OWN internal purposes;
  700-555-4141 is a universal number to determine one's line's chosen
primary carrier

500   US/CAN/CARIBB. "Personal Communications Services"
(Additional codes will be 533, 544, (but NOT 555), 566, 577, 588,

dPersonal communications service is defined more formally as "a set of capabilities that allows some combination of personal mobility, terminal mobility, and service profile management such as "follow me". It enables each personal communications service user to participate in a user-defined set of subscribed services and to initiate and/or receive calls on the basis of some combination of a personal number, terminal number, and service profile across multiple networks at any terminal, fixed or mobile, irrespective of geographic location.

800, 888, 877, and 866 - Toll Free
In 1993, however, the FCC began to permit some 800-number services to charge
for calls, provided that they have a "presubscription agreement"
with the caller.  A presubscription agreement is an agreement between a caller
and an information provider for future service -- and future billing.