xnormal- can be useful. I have baked in it once, but I only ever use it to extract a particular type of map that I use to draw the sharp highlighted edges in spec/diffuse maps, from baked normal maps.
if you can bake in your 3dapp/zb/mudbox, and use crazybump (which produce the best results) its not so useful for normal maps- though it might be wise to start using it over the nvidia normal filter if you still use that :shrug:
what phitt said- most free filters I have looked at are crap imo. I don't think I use any except those already included.
I have some custom brushes I like. a couple I made myself. Most were picked up over the years. I only regularly use about 15. Mostly scratch, grime, spill, dirt brushes. < phitt we should trade
also I have some mipmap profiles I like(sorta :S) for the nvidia dds plugin. I started experimenting with using GIMP for diffuse maps saving. Its easy to get a decent mipmap output, if you can stand using it, where as testing the many variables with the nvidia plugin gets tedious.
cs4 does texture projection, which actually looks useful. at the least it is not going to add a whole lot of extra arsing around to do a projection, and you'll almost certainly be in PS texturing anyway. It might be win.
(why does the spell checker flag texturing- it is most certainly a verb! it need to be a word
)