Radio - Usually the 1st form of communication developed by class 0-1 civilizations. Communications travel at the speed of light but take years to communicate across stars. Commonly used for close range communication within a solar system.
Subradio - Sends messages through all known radio frequencies simultaneously. This allows a conversation to go unnoticed by primitive worlds. While a class zero civilization such ours right now may listen to one frequency at a time, we may only pick up tiny parts of a message. The only way to understand the message is to listen to all frequencies at once.
Courier Messageing - In the time before a civilization invents FTL Communications, FTL travel via Courier ships are the only way to send messages and information across stars faster then sublight methods. Many interstellar civilizations would establish a large network of "Messenger Ships" to relay information back in forth across stars in a matter of days and hours. Instead of the years that it would have taken with normal radio/subradio communications.
Subspace - Usually developed sometime during a civilizations ascension to class 2 status. Essentially sends electromagnetic packages of data through hyperspace. These packages can hold anything from a simple "hello" to a full on schematic for an entire star ship. Allows near instant communication between the closest galaxies.
Darkwave - Used by class 4-5 civilizations. Uses the same type of technology of a loopwarp drive by manipulating dark energy to physically link two points in space. This allows instant conversation anywhere in the universe as long as you know the exact coordinates.