I found a great site with many unique free VSTs called Tweakbench. Tweakbench is an "audio software project" by one person, Aaron Rutledge, and offers free VST instruments and effects for windows VST hosts.
Right now the site has links to 14 Instruments (carillon dropout field minerva monomate padawan papaya peach pippo rebar ritual tapeworm toad triforce), and 8 Effects (breakdown cairo grumblebum maelcum mashup pudding sideslip yoink).
Peach is a synthesizer "based on the classic nintendo entertainment system's psg audio system. more than 30 waveforms from many memorable sounds and tones have been meticulously deconstructed and tamed." This is a fun little synth for sure and will make you reminisce about classic gaming music. Check out an MP3 sample.
As I mentioned all VSTs are free and have documentation. Note that you can get ALL the VSTs in a bundle for $5 (the 5 bucks to cover bandwidth costs).
If you really dig some of these VSTs and want to support this sort of development, Tweakheads accepts donations and are also selling t-shirts.