A planetarium software that shows a 3D simulation of the night sky
Stellarium renders 3D photo-realistic skies in real time with OpenGL. It displays stars, constellations, planets, nebulae and others things like ground, landscape, atmosphere, etc.
Jewish prayer times
Android application that displays list of halachic/halakhic times for Jewish prayers (zmanim and zmanei tefillot).
Java version of Stellarium.