<blockquote>Command line tools on the web. Try our research tools directly in your browser.</blockquote>

Play with bits in IEEE floating-point numbers

<blockquote>A collection of free single-purpose online tools for web developers...</blockquote>

TOC:
<blockquote>
I.Welcome
II.A Tree-Walk Interpreter
III.A Bytecode Virtual Machine
</blockquote>

A flamegraph generator for Postgres EXPLAIN ANALYZE output.

Nicely written illustrations towards various topics via IPython notebooks by Peter Norvig.

<blockquote>Code Shelter is a collective of volunteer software developers that aims to help with maintaining popular open source projects whose authors need a hand or don't have the time to maintain them any more. </blockquote>

<blockquote>Wandbox is Online Compiler</blockquote>
Support quite a few languages

<blockquote>This is the account, billing, and security management hub for sourcehut</blockquote>

Offered services: git hosting, mercury hosting, build service, bug tracking, mailing lists, manual & wiki, task automation, pastebin