Ogre Battle 64 Archive
The most comprehensive Ogre Battle 64 fan site. Updated in 2020.
World and Mission Maps
Game rips of the world map and each mission map, on VGMaps.com.
GameFAQS Game Guides
There are several valuable guides hosted on GameFAQS covering mission strategies, neutral encounters, character alignment, character recruitment, starting army, and more.
Let’s Play Archive: Ogre Battle 64
Let’s Play Archive hosts a written walkthrough with many screenshots and details about game systems.
Prima Ogre Battle 64 Player’s Guide
Archive.org hosts a scanned copy of the original Prima Player’s Guide. This guide is very detailed, but it also contains many errors. It can be helpful to new players, but keep in mind that it primarily guides you through one route of the game and misses a lot of the details. Blech san has documented all of the errors in a separate guide.
These fan sites are no longer updated, but they still contain valuable information.