HelenOS is an open-source microkernel-based multiserver operating system written from scratch. It runs on several different CPU architectures (IA-32, x86-64, SPARC V9, IA-64, PowerPC, ARM, MIPS). HelenOS prides in portability, modularity, clean design and coding style.

It does not mimic any existing system and it is not meant to be POSIX-compliant or UNIX-like at all. Just as an example, HelenOS does not support fork().

Rediscovered Fri May 3 15:15:31 2019, when I copied the following description:
HelenOS is a portable microkernel-based multiserver operating system designed and implemented from scratch. It decomposes key operating system functionality such as file systems, networking, device drivers and graphical user interface into a collection of fine-grained user space components that interact with each other via message passing. A failure or crash of one component does not directly harm others. HelenOS is therefore flexible, modular, extensible, fault tolerant and easy to understand.

yEd is a powerful desktop application that can be used to quickly and effectively generate high-quality diagrams.
Create diagrams manually, or import your external data for analysis. Our automatic layout algorithms arrange even large data sets with just the press of a button.

yEd is freely available and runs on all major platforms: Windows, Unix/Linux, and Mac OS X.

..is a gnome-shell extension that adds smart and user-friendly tiling window features to your gnome desktop, inspired by bluetile.

Read-eval-print-loop for various languages (APL, CoffeeScript, Scheme, ...), implemented as client-side Javascript program.

Time-based one-time-password (TOTP, RFC6238) generator for Java mobile edition.

The idea behind its design is that passphrase memorized by the user, along with their email address, can act as a complete, portable basis for a persistent public key identity and provide a full substitute for other key pair models, such as having the key pair stored on disk media (the PGP approach).

Found via http://blog.cryptographyengineering.com/2014/08/whats-matter-with-pgp.html

Interesting books and software about compiler/interpreter construction, including Scheme 9 from Empty Space and SubC.

Computer history collections: PDP-10 archive (includes the TECO Emacs), SIMH the computer history simulator and a copy of bitsavers, which contains lots of software and high-resolution scans of many documents (including e.g. data books of electronic parts).

HTTrack is a free (GPL, libre/free software) and easy-to-use offline browser utility.

It allows you to download a World Wide Web site from the Internet to a local directory, building recursively all directories, getting HTML, images, and other files from the server to your computer. HTTrack arranges the original site's relative link-structure. Simply open a page of the "mirrored" website in your browser, and you can browse the site from link to link, as if you were viewing it online.

Arguments for v7 vs v6.