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.
Auto Multiple Choice (AMC) is a piece of software that helps you to create and manage multiple choice questionnaires, with automated marking. Tests can be written in plain text or LaTeX. Automated correction and grading is performed from scans of the answer sheets using optical mark recognition.
GoCheapR is a browser extension to help you find the best deal on the Internet. It compares offers from thousands of stores, give you coupons codes, and finds hidden or private offers. It also gives you related sites when you are surfing and enhances your browser by adding to the "New Tab" a powerful multi-search tool.
PeerProject is a versatile peer-to-peer filesharing client and file manager. It's intuitive and aesthetic while supporting many networks and features, including BitTorrent, G2, Gnutella, eDonkey, DC++, IRC, HTTP/FTP, and more. It's a mainstream fork of Shareaza p2p, for Windows and WINE.
wger Workout Manager is a Web application that can manage your workouts, group them into schedules (A>B>C), and export them as PDFs or iCal files. It helps you keep a log of the weights lifted in the different exercises as well as your own body weight and can also create and manage your diet plans.