Material Maker - Cross-platform, procedural texture generation tool.
TextureLab - Free, Cross-Platform, GPU-Accelerated Procedural Texture Generator.
Filter Forge - On the surface, Filter Forge is just a Photoshop plugin, a pack of filters that generate textures...
Rectitude - Procedural generation pixel art editor.
PixPlant - A complete solution for repeating textures and 3D maps. Save a lot of texturing time with PixPlant!
Patternshop - Patternshop is a tool to create textures for fabric design.