gbrainy is a brain teaser game and trainer to have fun and to keep your brain trained. It provides logic puzzles, mental calculation, memory trainers, and verbal analogies.
Brain Workshop “is a free open-source version of the dual n-back brain training exercise.”
Websites: Lumosity helps you to improve memory, increase focus, and feel sharper and Human Benchmark, a website to test your brain.
Apps: Discover what you can do with Peak, the number 1 app to challenge your brain. Elevate is a brain training program designed to improve attention, speaking skills, processing speed, memory, maths, and more.
Chess.com. Play chess online with millions of players around the world! Enjoy free unlimited games and improve your chess rating with 50,000+ tactics puzzles, interactive lessons and videos, and a powerful computer opponent. An alternative is chess24 where you can play chess, learn chess, read chess news and watch chess live.
lichess.org is a free chess app to use for chess training. Lucas Chess is a chess program to train, play and compete, and it is open source. PyChess is a fully featured, nice looking, easy to use chess client for the Gnome desktop.
Chess in GNU/Linux: sudo apt-get install scid (a chess database application) stockfish (a powerful and open source chess engine). Play against the chess engine. Open scid and select Tools, Analysis Engine. Click on New… Name (stockfish), Command (/usr/games/stockfish -you need to check it with: which stockfish), Directory (click the ~/.scid button).
The GNUbik program is an interactive, graphical, single player puzzle. It is an implementation of the classic game that was invented by Erno Rubik.
Mind Mapping Tools:
XMind is a full-featured mind mapping and brainstorming tool, designed to generate ideas, inspire creativity, brings you efficiency both in work and life.
FreeMind, “is a premier free mind-mapping software written in Java.”
Coggle is an online tool for creating and sharing mindmaps and flow charts.
GitMind is an all-in-one free mind mapping and flowchart tool that inspires creativity and productivity.
Bubbl.us is an easy-to-use, online brainstorming and mind mapping software.
The CmapTools “empowers users to construct, navigate, share, and criticize knowledge models represented as concept maps.”
Diagram Tools: Dia is a free general-purpose diagramming software. diagrams.net is free online diagram software for making flowcharts, process diagrams, organization charts, UML, ER and network diagrams.