Astronomical software clock MAXCLOCK
The high-precision astronomical (software) clock displays various sidereal and solar time signals (for Greenwich and other selectable site), equation of equinoxes, Julian dates in UT1 and ET, Delta-T, Sun and Moon in aequatorial and ecliptic coordinates (milliarcsec-accuracy), and issues announcements for solstices, equinoxes, and Moon phases.
http://www.umark.de - Details

cio of universal concepts
free vertual telescope
http://www.stellarium.org - Details

MicroObservatory
• Optimize an image's brightness/contrast automatically, by either linear or logarithmic scaling. • Colorize images using several false color tables. • Invert an image's color table. • Increase image contrast and detail using "sharpen" filter. • Reduce the noise in an image. • Manipulate full screen magnification. • Show image information for individual pixels by cursor placement.
http://mo-www.harvard.edu/MicroObservatoryImage/ - Details

Observation Manager
Observation Manager is a free and open logbook for (amateur-) astronomical observations. It's written in pure Java and runs on every plattform supporting Java 1.4 or higher. All logbook entries made in Observation Manager are stored in the free and open COMAST XML Schema.
http://observation.sourceforge.net/en/ - Details

Little Windows Helpers
Yes, it is possible to write small Windows programs - but who cares? If you do, have a look at these programs written in PureBasic. They do not come with an installation program, and they do not make any entries in the Windows Registry. Just unzip the files to a program folder, and make a shortcut.
http://home.mnet-online.de/horst.muc/win.htm - Details