This may not be exactly what you're looking for but Electronics for Guitarists is a pretty good resource for understanding some of the ideas/theory/design behind everything from guitars to pedals to amps. Again not exactly what you're looking for but I recommend it to everyone with interest in this stuff.
My wall of text posts about asking for help will show that I'm still not an expert but the first book that really got me going was Electronics for Guitarists ( http://www.amazon.ca/Electronics-Guitarists-Denton-J-Dailey/dp/1461440866 )
It's not free unfortunately but it's the first book that I found delved at a good level into electronics but always from the perspective of a guitarist instead of an EE student. I do believe that learning something, especially something as complex as electronics, is much easier when in the right context, which for us, is guitar effects and amplification.
You won't find cookie-cutter recipies but you will find a lot of very simple circuits and their analysis and explanation. Also, the math is not required and you can skip it, but it's in there if you want it which I think is a good thing.
I think you can read a bit of chapter one about power supplies on Amazon. Take a look!
I see this question pop up every so often. As someone who has only just joined the wonderful community of pedal builders, here is what worked for me:
I believe the very first starting point of anyone wanting to get into pedal building would be to get a good grasp on the basics of analog electronics.
A couple months ago, I had virtually no knowledge whatsoever besides basic Ohm's law maybe. I started by watching a great video series by a guy named Martin Lorton. I found them easy to follow and, although they mostly just cover the basics, I was confident enough to push further afterwards. The first video is at: https://www.youtube.com/watch?v=F_5sV8s9ZEA
Then, I watched more videos on allaboutcircuits.com. I believe they are part of a college course. I reviewed most of what I'd seen in the MJLorton's videos and went a bit deeper. Here they are: http://www.allaboutcircuits.com/videos/index.html
At this point I was able to identify patterns on pedals schematics such as filters, clippers, transistor and opamp-based amplifiers. I had gotten myself a breadboard and a bunch of components like resistors, caps, transistors and diodes and tried reproducing the bazz fuss circuit - which I believe would be one of the simplest effect circuits possible. Here's a link to a good article about it and some mods: http://www.home-wrecker.com/bazz.html
Then, I followed up by reading even more articles but these went pretty far into the mathematics. A lot of people hate maths and I was no different. But once you can do things like, for example, calculate the frequency response of a filter, naturally, it all gets so much clearer. It's really worth the extra effort! You can find these more in-depth articles at: http://www.electronics-tutorials.ws/
You'll see, as you get more confortable, articles on Geofex, Beavisaudio, Muzique.com and the likes will start opening up and will suddenly get much easier for you to understand.
Today, after going at it for the most part of the last 17 weeks (according to the Instagram picture of my first circuit lighting a led), I've just finished building my first overdrive from scratch. It's a simple opamp buffer/gain + germanium diodes clipper with low and medium gain modes and a low pass filter for tone control. I obviously haven't invented anything new - but I started from nothing, played on my breadboard, drew the schematics, made the calculations, made it into a layout, assembled, rocked and boxed everything and I'm really proud of it!
A few days ago, I started reading Electronics for Guitarists by Denton J. Dailey. So far it's a very good read as it helps making parallels between all these things I've learned and their applications in the field of guitar-related electronics. I think it's a good investment if you have a couple extra bucks. Here's an Amazon link: http://www.amazon.com/Electronics-Guitarists-Denton-J-Dailey/dp/1461440866
Also, do not hesitate to ask for help on this subreddit. People have been very helpful when I had questions and have opened my eyes on critical things.
Good luck and, more importantly, have fun because it's a wonderfully addictive hobby!
EDIT: accidentally a paragraph
https://www.amazon.com/Electronics-Guitarists-Denton-J-Dailey/dp/1461440866/
i have it, but i'm too dumb to really understand and make use of it :(
Edit: you might wanna check out http://www.electrosmash.com/ as well