I am currently getting in to making textures for building things in Second Life and Blender. I use GIMP, Inkscape, and Krita. I find myself however googling for guides a lot and doing specific things then forgetting them. I have figured out a few things on my own (I can make nice grungy paper!), but would love to know of any small simple 'walkabouts' of programs that teaches you how to use layers and filters. I tried reading the big GIMP guide but didnt really give me examples of what can be done with all the filters etc.

Anyone know of any good texture making guides online or books?