Egosoft guides (patch notes are here)
Rebirth v1.25: features video.
Rebirth v1.30: Upkeep Missions video.
Rebirth v2.00 can guide is here.
Rebirth v2.50 Diplomatic Aid missions are explained in this video.
Rebirth A v3.00 feature guide is here.
Rebireth v3.50 Flight Assist OFF guide is here.
Player guides
Boarding by XenonSurf (link).
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NPC Small Talk & Trade Agents by Sparky Sparycorp (link).
NPCs for hire by euclid (link).