Here's a list of my favorite old school links that were a great reference to me when I was starting to build stompboxes in the late 2000's.
VINTAGE FUZZ
Uzzfay Fuzz Guts:
https://www.freestompboxes.org/members/uzzfay/web.archive.org/web/20120313025319/http_/members.fortunecity.com/uzzfay/home.html
Fuzz Central
https://fuzzcentral.ssguitar.com/
EXPERIMENTAL CIRCUITS:
Tim Escobedo's amazing circuits:
http://www.jiggawoo.eclipse.co.uk/guitarhq/Circuitsnippets/snippets.html
John Holis:
http://www.hollis.co.uk/john/circuits.html
The Tone God:
https://www.thetonegod.com/diy
INFORMATION and DIY PCBS
Tonepad:
http://www.tonepad.com/
General Guitar Gadgets:
https://generalguitargadgets.com/
Madbean, still going strong. MY favorite OG diy pcb retailer, great forum.
https://www.madbeanpedals.com/
Beavis Audio Reasearch. Probably my favorite site, learned how to breadboard from this site which is the greatest gift.
http://beavisaudio.com/
FORUMS
DIYSTOMPBOXES. The true OG to me. Started cruising here sometime in 2008. Even back then it was an endless treasure trove of information.
https://www.diystompboxes.com/smfforum/index.php?board=2.0#google_vignette
Freestompboxes. Another great forum. Great place to go to research specific pedals. https://www.freestompboxes.org/
I Love Fuzz. This was always my favorite place. Started selling pedals here and made many great friends here:
https://ilovefuzz.com/