50 MHz frequency counter, voltage meter & SWR/PWR indicator by S56AL
This is a successor of the PIC16C71 4-digit LED f-counter & V-meter. Some hard to find parts used in the previous version, which are out of production for some time, has been omitted. A rather early PIC16C71 has also been replaced by 28-pin device PIC16F876.
https://www.s56al.si/ham_radio/fc_led_2/fcl2.html

BCD readout frequency counter by GØUPL
This frequency counter isn't the easiest to read, nicest, best frequency counter you can build. But if all you can find is a few 74HC390 and some ordinary 5mm red LED's, it does the job and is easy and fast to make!
http://www.hanssummers.com/bcdfreq.html

Frequency Counter/Timer/Logic Tester by GØUPL
This was my first frequency counter project. It includes quite a number of useful testing features which were very useful when building other projects.
http://www.hanssummers.com/counter.html

HF marker by PA2RF
A useful tool I built in 1999 is an “HF Marker”. This simple device produces a 10 MHz primary signal and lots of harmonics (even and odd).
http://pa2rf.blogspot.com/2014/02/hf-marker.html

LCD Frequency Counter by GØUPL
This frequency counter module is intended as a "digital dial" frequency readout for portable QRP radio tranceivers. It uses only six standard discrete logic IC's, i.e. no PIC or other microcontroller, no programming to be done, etc.
http://www.hanssummers.com/lcdfreq.html

Low Cost Multifunctional Frequency Counter by VU2ITI
We are introducing a low cost multifunctional seven digit LCD frequency counter, for your HAM radio shack. This frequency counter is designed in such a way that it can be used for direct frequency measurement or with any of the commercial / home made radio/transceiver as a digital frequency display.
https://www.hamradio.in/projects/multifunctional-frequency-counter

Microprocessor based frequency counter up to 70MHz by DL5NEG
In order to make the circuit work, it is important to set the fuse bits inside the AVR micro controller correctly. Theses fuse bits can be set with the programmer that is used to flash the software.
http://www.herbert-dingfelder.de/?page_id=304

Radio Frequency Counter by GØUPL
This very tiny frequency counter was built to fit inside the front panel of a radio tranceiver. It now occupies pride of place in the front panel of my HF Receiver, alongside my panel mounting clock.
http://www.hanssummers.com/radiofreqcounter.html

Simple Frequency Counter by GØUPL
This is an incredibly simple and cheap frequency counter with binary readout, based on the ideas of Onno PA2OHH. I built two versions: one Mk1 "prototype" for development and optimisation of component values, ...
http://www.hanssummers.com/sfreq.html

The NorCal Frequency Counter, FCC-1 by W3CD
The NorCal FCC-1 is a highly flexible frequency counter that incorporates features not found in any comparable unit. Its small size allows it to be incorporated into your favorite rig and your battery will hardly notice its modest current requirement.
http://www.norcalqrp.org/files/FCC-1_Manual.pdf

Universal frequency counter & voltage meter by S56AL
For the purpose to be used with QRP transceivers I have developed some frequency counters with different types of displays (from simple 8 LED display to 2 x 8 character LCD), but the f-counter described on this page I have found to be the most useful.
https://www.s56al.si/ham_radio/fmtr/fmtr.html