Substance Designer - Substance Designer is a node-based non-destructive application for material authoring.
Material Maker - Cross-platform, procedural texture generation tool.
ShaderMap - Create Rendering and PBR Maps in Seconds!
TexGraph - Node-based, procedural texture creation tool for Windows.
PixaFlux - PixaFlux is a node based image processing application.
Filter Forge - On the surface, Filter Forge is just a Photoshop plugin, a pack of filters that generate textures...