Some interesting tools like binary diff, keyboard event capturer, CalDAV server or VoIP application.

Xdelta is a tool and library for differential compression, VCDIFF encoding and decoding and compressing 64 bit files.
Supports binary diff, it is fast and does not require huge memory even for big files.

Radicale is a small but powerful CalDAV (calendars, to-do lists) and CardDAV (contacts) server

* Shares calendars and contact lists through CalDAV, CardDAV and HTTP.
* Supports events, todos, journal entries and business cards.
* Works out-of-the-box, no complicated setup or configuration required.
* Can limit access by authentication.
* Can secure connections with TLS.
* Works with many CalDAV and CardDAV clients.
* Stores all data on the file system in a simple folder structure.
* Can be extended with plugins.
* Is GPLv3-licensed free software.