Astrophotography and image processing:
PIXINSIGHT - astrophotographer's image processing (link..)
IRIS powerful image processing (link..)
MAKALI'I - professional image handling, incl. FITS format (link..)
GIMP - commonly referred to as the free version of Photoshop! (link..)
Registax 4 - Astrophotography stacking (link..)
WhatsUp – A planning tool to help any Astrophotographer plan their night under the stars (link..)

Star charts and atlasses:
Cartes du Ciel - (Free) Detailed star chart generator (link..)
Skymap Pro - (Commercial) Detailed star chart generator (link..)
The Sky - (Commercial) Detailed star chart generator (link..)
Starry Night Enthusiast - (Commercial) Planetarium program and star map viewer (link..)
SFA Sky Charts - (Free) simple star maps (link..)
Virtual Moon Atlas - (Free) discover the moon from your desktop (link..)

Simulators & Planetarium software
Stellarium - (Free) one of the best night sky simulators available (link..)
Celestia - (Free) fly into the solar system and beyond... (link..)
GoogleEarth - go on a voyage of discovery from your PC (link..)
NASA World Wind - the Earth from space (link..)

Satellite Tracking
Orbitron - (Free) Satellite Tracker (link..)

Planispheres
Planisphere - (Free) make your own professional-looking planisphere (link..)

[Submit software links]