Official Files:
F.A.K.K.² Patches
F.A.K.K.² Tools (6.24Mb)

Mapping Files:
Goetzenzar's Special effects gallery (254 kb, all the fx_ entities in one map)
Map source for six original F.A.K.K.² Maps (1.6 Mb, kudos to ritual for this one)

Scripting Files:
None yet

Coding Files:
None yet

Modelling Files:
None yet

Texturing Files:
.FTX converters (62.7Kb) by Yorvik

Tutorial Specific files can be found at the bottom of that tutorials page.