Encyclopedia Mod 5.5
This repackages version 4.3 the extensive Encyclopedia Mod, which adds detailed information to the otherwise cryptic in-game descriptions. There're also tutorials and details of game mechanics.
It also includes a fixed version of BaseRelations.txt, which tweaks initial race relations in a more sane direction.
These mods are included in the MegaMod package; this is for those who prefer the original gameplay but still want the extremely useful Encyclopedia.
Classic and Mac OS X
Working install of Master of Orion 3, patched to v1.2.5.