Remember to check if the code is experimental, if it is updated and its corresponding license ;)
draw2d - http://www.draw2d.org/draw2d/ - diagrams (js)
alchemy.js (graph) https://graphalchemist.github.io/Alchemy/#/ - graphs (js)
wavesurfer.js - https://wavesurfer-js.org/ - audio waverform visualization (js)
leafletjs - https://leafletjs.com/ - mobile friendly interative maps (js)
flipclockjs - http://flipclockjs.com/ - clock (js)
magnifier.js - https://mark-rolich.github.io/Magnifier.js/ - zoom (js)
turn.js - http://turnjs.com/ - flip through pages (js)
citoscape - https://js.cytoscape.org/ - graphs and networks (js)
clusterize.js - https://clusterize.js.org/ - scroll large lists (js)
pyknotid - https://pyknotid.readthedocs.io/en/latest/# - analize knots (py)
howlerjs - https://howlerjs.com/ - audio (js)
networkx https://networkx.github.io/ - graphs (py)
jsnetworkx - http://jsnetworkx.org/ - graphs (js)
svg.js - https://svgjs.com/docs/2.7/ - svg manipulation (js)
jqueryUI - https://jqueryui.com/ - user interface interactions (js)
arborjs - http://arborjs.org/ - graph (js)
cleave.js - https://nosir.github.io/cleave.js/ - formatting input (js
JSMpeg - https://jsmpeg.com/ - video decoder for mpge1 and mp2 (js)
sigma.js - http://sigmajs.org/ - graph (js)
dracula.js - https://www.graphdracula.net/ - graphs (js)
plot.ly https://pypi.org/project/plotly/ - graphs and charts (py)
turf.js - https://turfjs.org/ - geospatial tool (js)
two.js - https://two.js.org/projects/ - lightweight 2d library (js)
three.js - https://threejs.org/ - lightweight 3d library (js)
cola.js - https://ialab.it.monash.edu/webcola/ - graph (js)
visjs - https://visjs.org/ - graph (js)
p5js - http://p5js.org/ - Processing adapted to javascript (js)
python object notation - https://bitbucket.org/ruamel/pon/src/default/ -pon
javascript object notation - https://json.org/ - json
highlight.js - https://highlightjs.org/ - sintax highlighting for the web (js)
gif.js - https://jnordberg.github.io/gif.js/ - gif (js)
d3js - https://d3js.org/ - graph and charts (js)
zoom.js - https://lab.hakim.se/zoom-js/ - zoom (js)
electron.js https://electronjs.org/ desktop apps from javascript,html and css
anypixel.js https://googlecreativelab.github.io/anypixel/ - interacive displays (js)
lazy.js - http://danieltao.com/lazy.js/ - functional programming helpers with a lazy engine (js)
chroma.js - https://github.com/gka/chroma.js/ - color manipulation (js)
validate.js - https://validatejs.org/ - validate js objects (js)
lighttable - http://lighttable.com/ - code editor
ninjaIDE - http://www.ninja-ide.org/ - code editor
tabulator - http://www.tabulator.info/ - interactive tables (js)
obelisk.js https://github.com/nosir/obelisk.js isometric pixel elements (js)
sphinx - https://www.sphinx-doc.org/en/master/ - documentation (py)
jsDoc - https://github.com/jsdoc/jsdoc - documentation (js)
graphp - http://graphp.com/ - graphs (php)
neDB - https://github.com/louischatriot/nedb/ - javascript database
taffydb - http://taffydb.com/ - javascript database
pyDbLite - https://pydblite.readthedocs.io/en/latest/# - python database
codernityDB - http://labs.codernity.com/codernitydb - python database
impress.js - https://impress.js.org/#/ - web presentation (js)
graph-tool - https://graph-tool.skewed.de/ - graphs (py)
fluidinfo.js - https://github.com/fluidinfo/fluidinfo.js - library for fluidinfo
fluidinfo.py https://github.com/fluidinfo/fluidinfo.py - library for fluidinfo
deep painterly harmonization - https://github.com/luanfujun/deep-painterly-harmonization - (py)
jeeves - https://github.com/jeanqasaur/jeeves - enforcing privacy policies (py)
soma.js - https://somajs.github.io/somajs/#/ - framework (js)
django - https://www.djangoproject.com/ - framework (py)
nette - https://nette.org/ - framework (php)
pyData - https://www.youtube.com/user/PyDataTV/videos - python videos
jsConference - https://www.youtube.com/user/jsconfeu/videos - javascript videos
scrapy - https://scrapy.org/ - web scrapping (py)
snap.py - https://snap.stanford.edu/snappy/ - graphs (py)
sticky notes - https://codepen.io/edmondko/pen/udcHG
GraalVM - https://www.graalvm.org/ - universal virtual machine
JavaScripthon - https://github.com/metapensiero/metapensiero.pj - a Python 3 to ES6 JavaScript translator
js2py - https://github.com/PiotrDabkowski/Js2Py - ECMAScript 5.1 to js
python-spider-monkey - https://github.com/davisp/python-spidermonkey - execute python from a js VM
transcrypt - http://www.transcrypt.org - Python in the browser, precompiled for speed
rusthon - https://github.com/rusthon/Rusthon - Python to Javascript
pypy.js - https://github.com/pypyjs/pypyjs - fast python for the web
brython - https://github.com/brython-dev/brython - in-browser python 3
skulpt - https://github.com/skulpt/skulpt - in-browser python 2
foreign function interfaces for js - https://emscripten.org/docs/porting/connecting_cpp_and_javascript/Interacting-with-code.html
foreign function interfaces for python - https://docs.python.org/3/library/ctypes.html
Node-Os http://node-os.com/ The first operating system powered by node.js and npm
Interface description languages and others :
apache thrift - https://thrift.apache.org/
babel - https://computing.llnl.gov/projects/babel-high-performance-language-interoperability/#page=home
messagePack - https://msgpack.org/
protocol buffers - https://developers.google.com/protocol-buffers/