Google Sky Map is a free app for Android phones, which uses your phone's compass, GPS, and clock to accurately display an exact diagram of what's above you. Point your phone to a specific area of the sky and you'll be able to pinpoint constellations, planets, and deep sky objects. If you're not quite sure where Mars is, simply search for it within the app and it'll help you locate it in the sky.
Pylone Starlight is a $50 flashlight that beams constellations onto any dark surface. You simply select the current month, day, and time using the rings on the light, and it will project the appropriate constellation locations so you can easily find them above you once you shut it off.
Sky Quality Meter is for those serious about their star gazing. Point the $120 unit in the area you want to check out stars and press the red button. A sensor reads back the amount of light detected in a 45 degree cone. The numbers range from 0 (bright) to 23 (pitch black). According to CloudyNights.com, "an urban sky will measure around 18 or 19 or lower on the SQM. A reading over a 20 is getting into 'fair' viewing conditions. A reading over 21 is getting into truly dark skies. Around a 22 is the most perfect sky you are going to get. At that point the SQM is measuring the stars and not skyglow. As a matter of fact I’ve seen the unit drop slightly as the Milky Way rose overhead."
Meteor Showers Yahoo! Widget notifies you when one of the eleven most visible meteor showers are active.
dSLR Shutter is a cross platform, freeware application that allows you to schedule long exposure shots from your dSLR camera. Just tether your dSLR to your laptop and set intervals and exposures you'd like your camera to snap photos of the sky with. A great app for photo enthusiasts that allows them to capture night shots without keeping their peepers peeled to their camera's viewfinder.
Satellite Flybys is an application available for both iPhone and Android mobiles that gives you a heads up (har, har) when a manmade craft can be seen up above. From the International Space Station to Hubble, there are tons of little bright lights that move across the sky that aren't stars or planets, but rather stuff we sent up and are now traveling around our orbit. This app gives you a countdown clock when a notable spacecraft is about to appear and tells you which direction you should face to see it!