I don’t have any links about multitexturing, but there are plenty of demos that use it from guys like Humus & Nutty, as well as IHV pages (nVidia / ATi).
Combining the results is generally done with TexEnv() calls (assuming you want to use the core features).
Look into the specs on the texture_env_* extensions, or maybe the core spec of GL 1.4, or again, demos around the net.