Using Qt to make it cross platform. Probably use libVLC for video playback (and I believe there is qt-vlc or vlc-qt or something like that for easy linking). May also look into OpenGL at somepoint, but we shall see how we get on.

Using Windows for development and MinGW as a compiler. For making I'm being lazy and just using qmake (at some point I might get round to making my own make file).