Bob Moog, if anyone, seems to earn the title 'father of the synthesizer'. While Hammond and many others contributed along the way, I think I can safely say that nobody else has created instruments which inspired new ventures in music like Bob Moog. His circuit and mechanical innovations were studied and copied by so many others. His instruments find a place in the mix and have given players new ways to express themselves in it I believe like none before him.
Considering that the MiniMoog was really the first easily portable true synthesizer, one would expect some crude, doofy sounding, poorly built thing that was crammed out into market to try to beat the next guy. Sorry Bill Gates...I have to mention your name here for...some reason. hehe. RATHER....these were finely constructed beauties that found their place immediately in progressive music and STILL are saught after as one of the finest monophonic synthesizers of all time! Check out these pics from the Moog Foundation!
As to his innovations, look at the Moog Patents link to get an idea of some of the landmark contributions to the field. Along with the MiniMoog, we see many great innovations in the PolyMoog, including the first fully polyphonic synthesizer (albeit with the crudest programming interface....soldering resistor packs together...ever constructed, in terms of editing the settings for the fully polyphonic aspects. :-) ), and the first velocity sensetive synth. The Moog ladder filter circuit became so saught after that many other companies released products that cloned it and some like ARP decided to change to their own filter after some discussion. My Russian Aelita has a Moog filter clone essentially even. Also check out Alpha Entek's page for some good tech reviews on Moog and other synths.
Minimoog Sonic Six Satellite Micromoog Polymoog Minitmoog Multimoog Taurus Prodigy Vocoder Liberation Opus-3 Source Concertmate MG-1 Rogue Memorymoog