Quixel mixer

https://quixel.com/mixer

Rapid texture creation. Blend, paint & sculpt tileable materials in no-time.

Materialize (win only), free ↓

http://www.boundingboxsoftware.com/materialize

Materialize is a stand alone tool for creating materials for use in games from images. You can create an entire material from a single image or import the textures you have and generate the textures you need.