A mini CW key by PY2OHH
We show here the project of a CW key where 90% is mechanical construction and 10% electronics (two solder junctions).
http://py2ohh.w2c.com.br/trx/cwkey/cwkey.htm

Converted-Mouse Paddle with a built-in Keyer by 7N3WVM
The built-in keyer is also homebrewed from scratch. ... I usually operate this paddle with the thumb and forefinger as is shown in the picture at the bottom.
http://www.qsl.net/7n3wvm/keyer-mouse.html

CW IAMBIC KEY by LY3LP

http://sa555.blogspot.com/2010/04/cw-iambic-key.html

CW keyer for foxes and beacons by PA3HCM
Beacons and foxes have to identify themselves. Although I could sit along all day with my morse key, transmitting my call, I wanted to have some automatic keyer.
http://www.pa3hcm.nl/?p=296#more-296

CW paddle by PA2RF
Unfortunately I do not "speak" morse. In the past I tried to learn it several times, but I never managed to control morse. For training excercises I once built a CW paddle. It is a rather easy design. You only need some unetched PCB and small material.
http://pa2rf.blogspot.com/2014/04/cw-paddle.html

Double Lever Paddle by PAØCMU
Wayne Mc Fee, NB6M created a simple and easy to build CW paddle made from PC-board. Using Wayne's idea as a foundation I designed a double lever version for iambic keying.
http://members.ziggo.nl/cmulder/paddle.htm

Five Cent CW key by OH7SV
 
http://www.saunalahti.fi/~hohtola/ham/five-cent-key/five-cent-key.html

Homebrew CW Paddles by AA5TB
I had long been needing a set of paddles for use during and field operations. In my junk box I had a switchcraft panel switch that had leaves that could be disassembled and I had thought of using it to make a set of paddles ...
http://www.aa5tb.com/paddles.html

Homebrew Paddles by LA6AKA
Here is a set of lo-tech morse code paddles that I built during a couple of days between Christmas and New Year. Don't build them yourself! They turned out to be really cruddy.
http://arj.nvg.org/ham/paddle1.html

Homebrew Paddle with a built-in Keyer by 7N3WVM
The built-in keyer is also homebrewed from scratch. ... The rest of the space is filled with a batch of lead sheets for the anchor. A careful watcher may find that LEGO blocks are used for the knobs.
http://www.qsl.net/7n3wvm/keyer-lego.html

JUMA-KEYER1 by OH2NLT & OH7SV
Miniature PIC microcontroller based keyer kit with convenient modes.
The kit includes PCB, componets, knob and ready programmed PIC microcontroller.
http://www.jumaradio.com/juma-keyer1/

NSH Electronic Keyer / CPO by VU3NSH
This circuit is an Electronic Keyer built with 4 IC’s and it can be used as Code Practice Oscillator (CPO).
http://www.hamradio.in/circuits/nsh_keyer.php

Simple CW keyer (elbug) by OH7SV
This is a CMOS 4000 series logic based keyer with Dot priority.
http://www.saunalahti.fi/~hohtola/ham/elbug/oh7sv-elbug.htm

Simple Paddle Keyer by SMØVPO
This is a circuit that I particularly like due to its simplicity and speed of construction. With this circuit, it is now possible to include a paddle keyer as an integral part of all, but the smallest, of QRP CW transmitters. It also satisfies my intense hate for CMOS!!
http://sm0vpo.altervista.org/use/simplek.htm

The NUEKey (A Touch Sensor Keyer Paddle) by W8NUE
 
https://www.qsl.net/w8nue/NUEKey.pdf