Windows: If you'd like to keep your shortcuts and favourite applications close at hand without jumping back to the Start Menu, Radian is an open-source application launcher that centres your favourite and frequently launched applications right around your mouse.
Upon right clicking Radian appears around your mouse as a circle divided into quarters and three rings. You can customise nearly every aspect of the presentation including what applications go in Radian's compartments, what colour the segments are and what kind of segment it is. Each of the quarters can be designated as a custom slice where you manually create the shortcuts, as a quick launch which will pull from the Windows' quick launch bar, as a desktop slice which will display frequently used desktop shortcuts or as a recent documents slice.
Radian is open source and Windows only. If you're looking for another take on mouse-centric application launching make sure to check out previously reviewed Magic Formation and Circle Dock. Have a favourite application launcher to share? Let's hear about it in the comments.