http://www.zarria.net/Displacement Map Creator
Want to add displacement to your existing models?
This tool creates a displacement map from your existing normal map.
Normal Map Actions for Photoshop
Actions for manipulating tangent-space normal maps
Rotate and flip normal maps without breaking them.
(Also has an interesting article
Normal Map Photography
A technique for creating normal maps from real world objects.
All you need is a camera and a flashlight. )
