The Pike documentation
There are a few different manuals to chose from. Remember that these are all work in progress, so check back regulary. Also, don't hesitate to give us feedback so that we can keep these document as work in progress.
The Pike tutorial is a good starting point for everyone new to Pike, though some basic programming skill is recommended.
Module tree reference
The module reference manual contains the documentation of all the documented modules, classes, functions, constants and variables, ordered in a tree structure for fast access.
Complete chapterized reference manual
The complete reference manual contains all available documentation of all parts of pike, in the form of a traditional chapter based manual.
Writing modules in C
While the Pike refdoc system does not yet cover the technicalities of how to extend Pike on the C level, we have some material for that though.