Documentation
An FAQ is under development.
Manual
The Speex manual provides an introduction to Speex and CELP coding, speexenc and speexdec information, libspeex API information, and miscellaneous format information.
API Reference
The Speex API Reference Manual provides information on programming with libspeex.
Standards
There are efforts underway to make Speex an IETF-blessed format; A draft of "RTP Payload Format for the Speex Codec" is available.