A powerful calculator that gives you all the functions of an electronic scientific calculator. Can draw 2D and 3D graphics and use the computer's power to make calculations faster. Linux's version is still pretty basic.
Great for personal accounting, allows to manage your financial movements via "double-entry" book keeping. Allows to structure your accounting plan in any way you want and allows to easily create cusomizable graphical reports.
A nice application, very complete that allows to do whatever is necessary to manage a small business's accounting: Invoices, Book keeping, etc... Free in its base version (Open Source), still includes all the needed functions, the more advanced versions have features that might not prove to be necessary.
Created as replacement for Windows's notepad, notepad2 is light, fast and essential. Has advanced features like Syntax highlighting, zoom and support for various encodings. Based on Scintilla Text Editor's (SciTE) code.
More famous under the name of SciTE, this is a very advanced text editor that supports a lot of programming languages and highlights their syntax. It's a software with an intruitive GUI, but allows for a deep customization too.
Known as "VI Improved", this is a text editor that works mainly from command line, but there is a GUI version too (GVIM). At the beginning might be difficult to use, but allows an extreme customization of the work environment. Includes syntax highlighting, macro creation, code folding, creation of snippets and abbreviations, tabs support... And this is only the beginning. Vim is CharityWare, the donations done to support the program are sent to Uganda for charity.
Many consider this (me included) the future of Vim. NeoVim is the product of a huge work: a complete extension and refactor of the famous editor. And most of all supports Async operations (Now supported in Vim 8 too): the heavier operations won't lock up the User Interface anymore. Among the many things in the works, there is a VimL -> lua transpiler, which could make this editor something really big. My favourite editor so far.
Another great application to create install wizards and software repacks.
WorkRave|A small application that assists the use in prevention and recover from RSI(Repetitive Strain Injury), periodically the program suggests small breaks and some exercises to stay stretched and healthy.|✓|✓|
|ClamAV|OpenSource Antivirus that can detect a good number of spyware and viruses, sadly there is no integrated realtime protection, Windows version is called ClamWin|✓|✓|
|Immunet|Born from ClamAV's engine, Immunet is a good Cloud-based Antivirus, small, fast and efficient. Requires an always-active internet connection to work.|✓|❌|
|Avast!|Very famous antivirus, available in its free version which offers a good protection, sometimes, mostly in summer, some Advertisements for the pro version will come out.|✓|❌|
|Avira Antivir|Another good antivirus, fast and lightweight. Advertisements for the pro version pop up every update, so they might be slightly annoying.|✓|❌|
|Comodo Internet Security|A good all-round security suite. Antivirus, Firewall and HIPS all-in-one for free.|✓|❌|
|Comodo Firewall|Really great firewall with default-deny protection, works generally well, very customizable, but I can't get Eclipse IDE with its Maven plugin to work when this firewall is installed.|✓|❌|
|ZoneAlarm Firewall|A decent firewall, does almost everything by itself, if you want to share some services online (like a minecraft server) you need to lower your protection level from "High" to "Medium".|✓|❌|
|Stellarium|A nice simulation of the night sky, with this you can take a look at constellations, planets and more. Graphics are really well-made.|✓|✓|
|KStars|Nice night sky simulation, a really complete planetarium that can get connected to a lot of telescopes.|❌|✓|
|Celestia|Kind of different from Stellarium and KStars, Celestia allows you to "navigate" inside space, with the chance to zoom into planets, reproduced in 3D in a very precise fashion.|✓|✓|
|SCUMMvm|A small software that allows to relive the old Point-and-click adventures on modern PCs, firstly the ones programmed with LucasArts's SCUMMU, like the first 3 chapters of Monkey Island, or Sam and Max: Hit the road.|✓|✓|
|DOSBox|Another small software that simulates a DOS machine, allowing you to play the old DOS games, like the first "Prince of Persia". Kind of hard to understand initially, has a very detailed introduction guide, that allows you to play already after a couple minutes.|✓|✓|
|VirtualBox|Oracle's virtualization solution. Many PCs in one, without issues.|✓|✓|
|GCStar|Allows to manage any kind of collection, like CDs, DVDs, YoYos, Electric Train models, etc... With extreme ease.|✓|✓|
|Conky|An extremely light system monitor.|❌|✓|
|Eclipse|A very good IDE to code in many programming languages.|✓|✓|