Non-magical concealment

[Godna]

How many ways are there to gain concealment for hiding in core+the complete series? Or at least can't be pierced with true sight?

[Starbuck_II]

How many ways are there to gain concealment for hiding in core+the complete series? Or at least can't be pierced with true sight?

Psionic Concealment aka Conceal amorpha, greater. But that isn't mundane if you wanted non-magic ways.

Concealing Amorpha isn't an illusion so can't be pierced by True seeing.

[Myrmex]

Smoke sticks.

[BRC]

The main method is simply to use your environment. Hiding in bushes, smoke, behind things, in deep shadows, ect.

[Godna]

Psionics isn't available and I'd perfer concealment that i can move with.

[Korivan]

Tower shield I belive. Use the fallen bodies of your enemies. The bigger the better...need good strength

[Fluffles]

Dust of Dissapearance.

[Dimers]

You can blind your enemies, or force them to look away from you (as with gaze attacks). And true seeing doesn't pierce fog effects.

Also, I realize you said "core+splat", but your DM might be convinced to go for a General feat with significant prereqs that happens to be found in the XPH. It's called Cloak Dance:

CLOAK DANCE (GENERAL)
You are skilled at using optical tricks to make yourself seem to be where you are not.
Prerequisites: Hide 10 ranks, Perform (dance) 2 ranks.
Benefit: You can take a move action to obscure your exact position. Until your next turn, you have concealment.
Alternatively, you can take a full-round action to entirely obscure your exact position. Until your next action, you have total concealment.