I hope you can find something that helps you! :)
Blinkyparts Wiki
Wiki collecting information about Blinkyparts’ workshops and soldering kits.
Casper Electronics
The website got hacked in 2017 and rebuilt from scratch, but old versions containing the diy-related stuff have been archived and can be found in the wayback machine.
Ciat Lonbarde
Well-known name in the diy synthesizer community.
Has made some changes to the page over time. You might stumble upon dead links from forums. If that happens, try adding an additional ciat-lonbarde after the domain name, e.g. where https://www.ciat-lonbarde.net/paper/man/index.html returns a 404, https://www.ciat-lonbarde.net/ciat-lonbarde/paper/man/index.html will work.
Experimentalists Anonymous DIY Archives
Experimentalists Anonymous has been an online resource and information repository for people interested in building their own audio circuits since 2003.
The board seems gone, yet the archive remains.
LINES
A gathering place for discussion about sound, process, art, and related technology; our areas of focus in the public spaces. To foster the exchange of ideas: an in-depth response to a newly discovered album, or a possible solution to a common programming/patching issue, or a curious use of toasted pumpkin seeds and mango (you can easily mute categories and topics that are outside your interest.)
Look Mum No Computer
British musician and content creater who keeps a public list of his projects, complete with schematics etcc.
Look Mum No Computer Channel
YouTube channel to showcase Look Mum No Computer projects and music videos.
Look Mum No Computer Forum
Community mainly focused around the Look Mum No Computer diy projects.
Mod Wiggler
Online community focussing on a range of topics in the realm of digital music. This includes diy projects as well.
Has been remaned from "Muff Wiggler", but links using the old domain redirect correctly.
Peter B
Peter Blasser’s YouTube channel, showcasing ideas and instruments.
Peter B: Just B
Peter Blasser’s blog, which is still active as of today.
Schweizerische Gesellschaft für Mechatronische Kunst
Swiss group of people focused on diy electronics, workshops and events.
Swiss Mechatronic Art Society Wiki
Wiki collecting information on events and workshops, as well as the projects built there.
Synth DIY Wiki
This is a wiki that anyone can edit. It is a community wiki for learning and sharing knowledge about synthesizer do it yourself, i.e. designing, making, modifying or repairing electronic musical instruments and related equipment. The emphasis is on audio electronics and the technology of electronic music.
WarrantyVoid (Weltenschule TableHooters)
A pretty old website with a collection of all kinds of information on thoroughly inspected toy keyboards and often times their modifications.
World's easiest oscillator! Introducing the CD40106
Dusting off the old Heathkit to play around with some oscillators based on the CD 40106 Hex Inverter IC. Take an inverter, add a resistor and a capacitor and you have an oscillator :)