One of my favorite apps for my iPhone is an astronomy program I have called "Star Walk". It's an interactive visual map of the approximately 10,000 stars and "Messier Objects" in our sky that have an "apparent magnitude" of 6.5 or brighter (the lower, the brighter)*.
Basically, that's everything visible to the naked eye.
Since I do not own a telescope, it's perfect for me. Ever wonder where Vega is, or where in the sky you can find Cetus the Whale at a given time? Or when Venus is going to rise? It's in there! You can see the great spiral galaxy in Andromeda, M31, with it's hundreds of billions of suns, shining away and looking by eye just like a single star (it has an apparent magnitude of 4.5 from here, because it's more than 2 million light-years away!).
You can also go back or forward in time to see what the sky looked like "somewhen" else. And since the program is location-aware, the view you get is correct for the exact spot you are in, or any other you wish to choose.
So I've gone back in time to April 14th 1912, in the North Atlantic, to see that the new moon did indeed make it a very dark night for seeing icebergs.
The picture shows what the eastern sky looked like at the moment of my birth, as seen from the location of Mt. Carmel Hospital in Detroit. Looks like Venus, Jupiter, and Mercury were all there to check me out :)
* The magnitude scale is logarithmic, a first magnitude star is 100 times as bright as a sixth magnitude star. Amazingly, the Hubble Space Telescope can resolve objects down to an apparent magnitude of 30!
If you happen to have a big telescope or extreme curiosity, and easily visible stars don't cut it, try the USNO-B1.0 catalog. It is the most complete full-sky database, including more than a billion objects in various optical bands. It is considered accurate down to magnitude 21, far far below what we could ever see unaided.
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