Tom's Digital speaker project - Low cost Digital speaker implentation
Chris's DSP page - DSP crossover hardware development
Art Ludwig's Digital Filter page - Some interesting theory and applications
Anders Torger Digital Filtering - BruteFIR fast Convolution algorithm
Mark Hayenga's DSP based crossover
University of Essex - Audio Research Labs - The home of Malcolm Hawksford, Audio Guru
Steven W. Smith's Guide to Digital Signal Processing
Linkwitz Lab - Loudspeaker Design
Bob Stout's DIY Loudspeaker Driver Selection Guide
Mass Technologies - Vifa-Scanspeak - lots of good Vifa data sheets at Mass site too
War Audio - Focal Cabasse Raven
Paget Audio - MorelUSA / Morel(Israel)