QMentat helps you practice mental arithmetic. It uses arbitrary-length fixed point arithmetic, and can handle any size numbers, only limited by the size of your screen (and in the case of division with an integer result, the speed at which the number can be factored). It is also quite configurable, allowing you to tailor the questions to your needs.
SourceNote is a program for taking notes. It lets you add text, pictures, and your own drawings, all of which are packed into different boxes which you can move around, making organization easier. The interaction is optimized so that you can switch easily between your opened tabs, as in a browser.
Multiple Eyepairs Only is a project to define a file format and to provide tools to use cryptography for things like four-eyes principles. The key idea is this: if information should only be accessible to a group of people together, with the additional possibility to have some redundancy in participants, then MEO is for you.
parsical is a Shehensai or parsi calendar application. It's useful for prayers, birthdays, weddings, navjotes, jashans, and other events. It features sunrise calculation based on the computer timezone (as roj begins at sunrise in this calendar), "previous" and "next" month and year buttons, conversion between Gregorian and Shehensai dates, and jumping to the calendar month on a given date or roj.