The texture functions included in Texture Maker are available from a variety of software, both free and commercial.
For normal maps, you can convert grayscale bump/displacement maps to normal maps with the NVIDIA plugins for PhotoShop. You'll need their plugins anyway to load and save .dds files. If you want to go deeper into it, look at: ShaderMap Pro, CrazyBump, xNormal, and nDo. Or create the surface in a 3D modeler and bake it.
For creating procedural textures, see the http://forums.xonotic.org/showthread.php?tid=93. Although the list is quite long, it doesn't include the texture generators included with 3D modelers. Blender's procedural texture generator is now graphical node based. Arguably the most versatile free procedural texture/material generator is the one that's part of AOI (Art of Illusion). It has a very steep learning curve, but once you get past it, you can create almost anything.
If you are lucky enough to have an older version of PhotoShop that includes ImageReady, that will satisfy most of your seamless texture needs. If you want more, check Texture Studio and Seamless Texture Generator. If you are fluent in C++, the source code is available for Texture Studio.
About the only other thing that Texture Maker does is unskew images of surfaces that were photographed at an angle. You can do that with Inkscape which is also a good complement to PS for drawing/painting textures anyway.