Several extensions to potentially include

[tannerlegvold]

EDIT: I have also recently discovered https://github.com/ml-tooling/best-of-jupyter. Its basically this repo but better

By checking my Github Explore suggestions a few times a week I have amassed this list of extensions, all of which are not in this repository and should be considered for addition. I haven't used all them myself: quality may vary.

Spreadsheets

https://github.com/krassowski/jupyterlab-spreadsheet-editor
https://github.com/quigleyj97/jupyterlab-spreadsheet

Widgets

https://github.com/idom-team/idom - an alternative to ipywidgets that better adheres to front end design norms, learn more here https://towardsdatascience.com/the-new-age-of-jupyter-widgets-cc622bee2c4b

Spellchecker

https://github.com/jupyterlab-contrib/spellchecker

Background Info Display

https://github.com/jupyter-server/jupyter-resource-usage
https://github.com/deshaw/jupyterlab-execute-time
https://github.com/jtpio/jupyterlab-system-monitor
https://github.com/jupyterlab-contrib/jupyterlab-topbar

Coding Utility

https://github.com/jupytercalpoly/jupyterlab-interactive-dashboard-editor
https://github.com/jupytercalpoly/jupyterlab-code-snippets
https://github.com/lckr/jupyterlab-variableInspector

HTML Editor

https://github.com/timkpaine/jupyterlab_iframe
There are others listed in the above link

Other

https://github.com/mwouts/jupytext - converts notebooks to text and text to notebook allowing for easy interaction with merging, diffs, other editors, etc. Comes with an extension
https://github.com/jtpio/jupyterlite - a way to run Jupyter fully in the browser, so that no installation of anything is required
https://github.com/jupyterlab/retrolab - a "distro" of JupyterLab with extensions and configuration to give a simple "classic notebook" look and feel out of the box

Themes

https://github.com/arbennett/jupyterlab-themes
https://github.com/timkpaine/jupyterlab_miami_nights
https://github.com/AllanChain/jupyterlab-theme-solarized-dark
https://github.com/yudai-nkt/jupyterlab_city-lights-theme

[tannerlegvold]

QuantStack also has several repos including ipysheet, ipytree, and ipygany.

This is also a neat article (though it is from 2018) showcasing some ipywidgets functionality.