This post is a wiki - please feel free to add/edit as needed (please follow the same format/alphabetical order).

ash - https://www.in-ulm.de/~mascheck/various/ash/

A lightweight (92K) Bourne compatible shell. Great for machines with low
memory, but does not provide all the extras of shells like bash, tcsh, and
zsh.

bash - https://www.gnu.org/software/bash/

an sh-compatible shell that incorporates useful features from the Korn shell
(ksh) and the C shell (csh). It is intended to conform to the IEEE POSIX
P1003.2/ISO 9945.2 Shell and Tools standard

Bourne shell - https://en.wikipedia.org/wiki/Bourne_shell

Developed by Stephen Bourne at Bell Labs, it was a replacement for the Thompson shell

CMD.EXE - https://en.wikipedia.org/wiki/Cmd.exe

is the default command-line interpreter for the OS/2, eComStation, ArcaOS,
Microsoft Windows (Windows NT family and Windows CE family), and ReactOS
operating systems

COMMAND.COM - https://en.wikipedia.org/wiki/COMMAND.COM

is the default command-line interpreter for MS-DOS, Windows 95, Windows 98 and
Windows Me. In the case of DOS, it is the default user interface as well.

csh - https://en.wikipedia.org/wiki/C_shell

The main design objectives for the C shell were that it should look more like
the C programming language and that it should be better for interactive use.

fish - http://fishshell.com/

a smart and user-friendly command line shell for Linux, macOS, and the rest of
the family.

Hamilton C shell - https://hamiltonlabs.com/Cshell.htm

a complete Unix shell environment for Windows

ksh - http://kornshell.com/

You can write programs to run faster with ksh than with either the Bourne
shell or the C shell, sometimes an order of magnitude faster. ksh has evolved
and matured with extensive user feedback.

Nushell - https://www.nushell.sh/

a shell that uses pipelines and structured data to control any operating system

pdksh - https://en.wikipedia.org/wiki/KornShell#Variants

PD-ksh is a clone of the Korn shell

PowerShell - https://learn.microsoft.com/en-us/powershell/

PowerShell is a cross-platform task automation solution made up of a
command-line shell, a scripting language, and a configuration management
framework. PowerShell runs on Windows, Linux, and macOS.

Qshell - https://en.wikipedia.org/wiki/Qshell

A shell on the IBM i operating system based on POSIX and X/Open standards

rc - https://doc.cat-v.org/plan_9/4th_edition/papers/rc

is a command interpreter for Plan 9 that provides similar facilities to UNIX’s
Bourne shell, with some small additions and less idiosyncratic syntax.

Scsh - https://scsh.net/

an open-source Unix shell embedded within Scheme

tcsh - https://www.tcsh.org/

C shell with file name completion and command line editing

Thompson shell - https://en.wikipedia.org/wiki/Thompson_shell

the first Unix shell, introduced in the first version of Unix in 1971, and was
written by Ken Thompson

zsh - https://www.zsh.org/

a shell designed for interactive use, although it is also a powerful scripting
language