FET is a program for automatically generating timetables for schools and universities.

Typically, FET is able to solve a complex problem in a maximum of 5-20 minutes. For simpler schedules, this may take less time (a few seconds in some cases). For extremely complex schedules, this may take longer and may take several hours.

Caliber is a library for cataloging e-books. Includes library management, eBook viewer and editor, and synchronization features for eBook reading.
Allows you to convert e-books to a dozen different formats and back.
Supports synchronization with almost all e-book reading devices (for example, Kindle, Kobo, Nook).
Can automatically pull news from a range of websites/RSS feeds, format the news into an e-book and download to a connected device.

Gramps is a program for genealogical research. It is an extremely flexible program that meets the needs of both the amateur genealogist and the serious genealogical researcher. Allows you to store, edit, and research genealogical data.
Has the ability to import GEDCOM files exported from many proprietary genealogy programs and can generate a large number of reports in many popular formats. This allows any piece of information to be entered directly into Gramps and any event to be manipulated across the entire database (in any order), helping the user research, analyze and find connections with the ability to fill gaps in relationships.

gImageReader is a simple interface for tesseract-ocr. Tesseract is probably the most accurate open source optical character recognition (OCR) software available and can recognize text in over 60 languages.

It supports automatic detection of page layout, but the user can also manually define and configure recognition areas. You can import images from disk, scanning devices, clipboard and screenshots. Supports multi-page PDF documents. Recognized text is displayed directly next to the image, and basic text editing is possible, including search/replace and removing line breaks. Spell checking of output text is also supported if appropriate dictionaries are installed.

Xournal++ - Create handwritten notes, sketches and journaling with a stylus. From solving a physics problem to keeping travel diaries. It can also be useful for adding annotations to PDF files.
Supports pressure-sensitive styluses and digital pens (e.g. from devices such as Wacom tablets, Huion tablets, XP Pen, etc.)
Possibilities:

Gobby is a collaborative editor that supports multiple documents in one session and multi-user chat. This means that it gives you the ability to edit files simultaneously with other users over the network.

Valentina Studio provides the ability to create, edit, SQL queries, import and administer popular databases: Valentina DB, MySQL, SQLite and Postgre SQL using the following tools:
- diagram and diagram editor
- data editor
- SQL editor
- administration, diagnostics, compression, cloning, database defragmentation
and much more.

qStopMotion - creating frame-by-frame animated films from images imported from a camera or computer.

The resulting animation can be exported to various video formats, such as mpeg or avi.

Scratch is a simple, interactive, collaborative software development environment for creating interactive stories, animations, games, music, and graphics—and publishing them on the Internet. Scratch is designed to help children (ages 8 and up) implement 21st century educational skills. As they create Scratch projects, children learn important math and computer concepts and gain a deeper understanding of the design process.

U++ is a cross-platform rapid application development environment in C++. Can work with GCC, Clang, MinGW and Visual C++ and contains a full-featured debugger.
Fast development comes from smart and aggressive use of C++, not fancy code generators. In this regard, U++ competes with popular scripting languages while retaining the runtime characteristics of C/C++.
The development environment includes BLITZ build technology for up to 4x faster C++ rebuilds, visual designers for U++ libraries, Topic++ for documenting code and creating rich text resources for applications (such as help and code documentation), and Assist++, a powerful C++ code analyzer , which provides features such as code completion, navigation, and transformation.