Kanon (カノン)

Kanon (カノン) is a Japanese adult visual novel developed by Key and released on June 4, 1999 for the PC. An all ages version for the PC was released in January 2000, and was later ported to the Dreamcast, PlayStation 2, and PlayStation Portable. The Kanon Standard Edition was released for the PC in November 2004 playable as a DVD-ROM in adult and all-ages versions; this version incorporates the few extra graphics added to the earlier all-ages version of the game. Both Standard Editions add support for Windows 2000/XP and other technical changes such as more save slots. Otherwise, the all-ages Kanon Standard Edition is the same as the original all-ages version released for the game.
Starting in 2006, Kyoto Animation, the animators of another Key game-turned-anime, Air, decided to animate a new adaptation of Kanon. This 2006-2007 version aired between October 5, 2006 and March 15, 2007 on the Japanese television broadcasting station BS-i, containing twenty-four episodes. In a magazine published interview, studio producers stated that the primary reason for considering animating another Kanon anime was largely in part due to Kyoto's Air anime being well-received by viewers. In the second episode of Air, in fact, the studio procured the rights and the original voice actors to give Ayu, Nayuki and Makoto a cameo as Kano Kirishima's school friends. Consequently, Kyoto Animation received numerous phone calls from viewers expressing their desire for the studio to animate Kanon. ADV Films announced on September 21, 2007 at the Anime Weekend Atlanta anime convention that they have officially licensed the second Kanon anime series. ADV had previously posted a trailer for the series in August 2007, but was soon taken offline once the news had been spread on the Internet. The first English-dubbed episode was made available via streaming online at Anime News Network between December 23, 2007 and December 30, 2007. In July 2008, the licensing rights of the second Kanon anime were transferred from ADV to Funimation Entertainment who will continue to produce the series in North America.

# Reference
http://en.wikipedia.org/wiki/Kanon
Kanon: The Complete Series(Amazon.com)