xEdit - Introduction to xEdit, which will allow you to understand how plugins work and how you can edit records.
xEdit Video - A good video by cloudisms that covers multiple parts of xEdit.
The Method - Guide on how to use The Method, which is used while creating a modlist in order to patch it properly and hide remaining conflicts that need no intervention.
Safe Modding - List of many outdated/dangerous mods and tools.
GECK Wiki - Community continuation of Bethesda's GECK wiki, maintained by NVSE modders; focused on GECK, scripting and game's inner workings.
Independent Fallout Wiki - Fan project focused on maintaining a high-quality, comprehensive and accessible encyclopedia about all aspects of the Fallout games, community and mods.