Coalition of Planets
The Coalition of Planets was a loose alliance of several planetary systems meant to provide mutual military, logistical, and humanitarian (!) support that formed in 2155. The Coalition was the result of a conference called by United Earth minister Nathan Samuels to discuss Romulan attempts at destabilizing and manipulating interstellar events. This conference was held at San Francisco, Earth.
Many of the planets invited to attend would go on to become founding members of the United Federation of Planets that formed six years later to supercede the Coalition. Some of those joining where:
The Andorian Empire
The United Colonies of the Rigel System
The People's Republic of Coridan
After the Romulan attack on Coridan Prime later in the year, the Coridanites opted not to join the Coalition. The attack also prompted Rigel to withdraw. Draylax and Alpha Centauri agreed to join soon after.
(Reference: Enterprise--"Demons"; "Terra Prime")