This is a collection of some of my favorite synthesizer links. It is not meant to be complete; there's a lot of material out there, so I'm limiting this list to historical documents, original work, well-referenced work, and my own personal likes. For instance, there are a lot of schematics available on the web for filters derrived from the Moog VCF; I won't be tracking these.
Many of these links are from the "Synth DIY" crowd, a community of electronic music enthusiasts who have collected together on the internet to share electronic design ideas and build synthesizer modules. Interestingly enough, over three decades after Robert Moog introduced the modular music synthesizer, and over 15 years after most electronic music companies have abandoned the field, these folks are making some impressive advances. A vintage technology revival? No, just building a musical instrument with the appropriate technology.