Analog Vocoder information: Specifications and reviews of vintage hardware vocoders.
Doepfer A-129: Modular 13-band vocoder designed for the A100 modular synthesis system.
Electrix WarpFactory: MIDI controlled hardware device, several audio demos available.
Korg MicroKorg: Synthesizer with integrated 8-band vocoder and microphone.
PAiA Vocoder: Inexpensive rack mount kit designed by Craig Anderton.
Vocoders and Vocoder-Derivatives: Detailed description of how vocoders work as well as ways of improving results.