To my knowledge, Jamie Heilman, aka "Leper", set up the first effects repository on the net. Jamie started up an effects schematic swap group by email, pooling the schematics from a group of effects crazies that he met on the then-non-commercial newsgroups. This is how I ran into him. The schematics swapping group was fairly well along when Jamie got space for a web page through his college. He decided to put the schematics on his new web page. Jamie and I contributed roughly half and half of the schematics that were in that repository. The whole mess of schematics was later donated to the ualberta circuits archive, where it remains today.
Jamie later ran out of storage space for all the data, and sent a copy of the whole mess to Jack Orman, who put them in toto on his DMZ. Jamie's whole page was mirrored for a time at a couple of places on the net, but I can no longer find those. Jamie's page, the Musical Electronics Micro Archive, remains on the web, but has had no updates since late 1996. I understand that his time is so consumed that he can't do updates.
From there, several other places have popped up. Some are just mirrors or partial mirrors of Leper's site. Some do and some don't credit the source. Recently, a few sites have sprung up that have actually added new schematics. Notably among these for good content are Justin Philpot's page, Aron Nelson's page, Stellan's page, Robin Tomtlund's page. Jack Orman's page has since removed all of the schematics from the MicroArchive in favor of a few other oldies and some new construction projects.