Sjöström Audio

http://www.vinylzone.com/phonopre.asp
Interesting RIAA correction amp with an OPA637 as main part. The designer is Thorsten Lösch (or Loesch) alias Kuei Yang Wang.
http://sound.whsites.net/project115.htm
Rodd Elliott's implementation of the so called Gainclone, long before the Gainclone concept was invented. It's LM3876 based but LM3886 will also fit. Boards are available.
http://leachlegacy.ece.gatech.edu/lowtim/
Professor W. Marshall Jr. Leach have designed a very interesting power amp with high slew rate.
http://pmacura.cz/audiopage.html
Pavel Macura has made a couple of very nice amplifier designs. He sells also pcb's.
https://ptodorov.com/the-blog/
Personal DIY blog of Plamen Todorov. Sharing my DIY builds of solid-state amplifiers, DACs, preamplifiers, cables and other DIY electronics.
http://waltjung.org/PDFs/WTnT_Op_Amp_Audio_1.pdf
This circiut is called diamond buffer or Jung super buffer (because of this article in the subject). The buffer can be used after an opamp with or without feedback, altough feedback is recommended. Part 1.
http://www.ampslab.com
"Lot's of kits here, such as power amps and even the famous and patented Alexander amp.You can also download a better copy here http://www.sjostromaudio.com/hifi_files/misc/AN211_better_text.pdf"
http://diyAudioProjects.com
DIY Audio site which contains a wide variety of DIY projects which include speakers, amplifiers and preamplifiers (chip, tube, solid state) and cables. You can also find a forum.
http://tangentsoft.net/audio/
DIY headphone amps, META42 and PPA called. One of the best designs for the DIY community. Very nice looking pcb's for sale. The amp is similar to my SMD QRV-04.
http://home.pacific.net.au/~gnb/audio/lm4780.html
In-depth technical information about the LM4780 stereo 60W chip and my design log for building audio power amplifiers using this dual-LM3886 equivalent. I also have a detailed comparison of specifications between the LM1875, LM3875, LM3886 and LM4780...
http://www.klaus-boening.de
This german guy is dedicated to tube amps and vinyl. He has also designed a very interesting balanced RIAA phono amp and also a turntable.
http://www.customanalogue.com/diytubegainclone/index.htm
The original "Tube Gainclone for DIY Buffs" website by Joe Rasmussen. Inverted GC with Tube Buffer and interesting features, such as LPF to shape bandwidth and tweak sound character (better soundstaging), zero feedback above 200KHz. Extensive spectral...
http://twistedpearaudio.com
Twisted Pear has a very nice looking Gainclone and also other stuff like preamps, attentuators, input selectors. They sell kits and pcbs. DAC is also in development.
http://winsome-labs.com
Tripath amplifier available kit or assembled. 45 W per channel Tripath amplifier, quality build with small size. Sold in bot h kit and assembled form.
https://www.hifiberry.com
HifiBerry has various DIY stuff usch as DAC's preamps, RIAA amps, power amps, power supplies etc.
http://www.lcaudio.com
DIY hifi stuff designed by Lars Clausen. They sell ready made units and pcb's. Not very cheap but on the other hand the quality is high industrial standard, not the common consumer standard.
https://www.amb.org/ti/audio/analog-b.html
Mr. Ti Kan has made a very nice turntable. Please notice that the website has frames.