libnoise, a portable coherent-noise-generating library for C++ compilers, has been released to the public for beta testing. Download the beta at http://libnoise.sourceforge.net/downloads/index.html.
Come visit our site at http://libnoise.sourceforge.net/. Here, you can view some examples of using libnoise to generate procedural textures and complex terrain. There are also several tutorials available to get you started.