Even if you have a telescope and access to a clear sky every night, Stellarium is worth your disk space. Learn, in an interactive way, positions of stars (600 000 in the database!), constellations, nebulas (full Messier catalog), planets and their moons. An excellent way to introduce someone, or even self, to the astronomy.
Tammy Plotner presents one of the most magnificent galaxies visible on our sky - Messier 31, also known as The Andromeda Galaxy. Fun fact from the article - in the distant future, the Milky Way and the Andromeda will merge; the Messier 31 is approaching our galaxy at 300 kilometers per second. But do not worry - we are safe for a several billion years from the date.