Star Chart - Stellarium is a planetarium software that shows exactly what you see when you look up at the stars. It's easy to use, and free. Read more about Star Chart.
Stellarium - Stellarium is a free open source planetarium for your computer.
Google Sky Map - Google Sky Map is a free hand-held planetarium that allows you to identify stars, planets and more.
KStars - KStars is a Desktop Planetarium for KDE.
Code NASA - 253 NASA open source software projects
SkyView - SkyView is powerful, easy-to-use app that answers questions about stars, constellations, and more.