The Cyrillic script is named after Saint Cyril, a missionary from Byzantium who, along with his brother, Saint Methodius, created the Glagolitic script. Modern Cyrillic alphabets developed from the Early Cyrillic script, which was developed during the 9th century in the First Bulgarian Empire (AD 681-1018) by a decree of Boris I of Bulgaria (Борис I). It is thought that St. Kliment of Ohrid, a disciple of Cyril and Methodius, was responsible for the script. The Early Cyrillic script was based on the Greek uncial script with ligatures and extra letters from the Glagolitic and Old Church Slavonic scripts for sounds not used in Greek.
The letters also had numeric values, the order of which cames from the Greek alphabet.
This chart shows most of the Cyrillic letters currently in use, plus ones that are no longer used, with their names.
The Cyrillic alphabet has been adapted to write more than 50 different languages, mainly in Russia, Central Asia and Eastern Europe. In many cases additional letters are used, some of which are adaptations of standard Cyrillic letters, while others are taken from the Greek or Latin alphabets.
Abaza, Abkhaz, Adyghe, Aghul, Akhvakh, Altay, Andi, Archi, Assyrian / Neo-Assyrian, Avar, Azeri, Bagvalal, Balkar, Bashkir, Bats, Belarusian, Botlikh, Budukh, Bulgarian, Buryat, Chamalal, Chechen, Chukchi, Chuvash, Crimean Tatar, Dargwa, Dungan, Enets, Erzya, Even, Evenki, Gagauz, Godoberi, Hinukh, Hunzib, Ingush, Interslavic, Itelmen, Kabardian, Khinalug, Juhuri, Kalmyk, Karaim, Karakalpak, Karata, Kazakh, Ket, Khakas, Khanty, Khwarshi, Kildin Sámi, Komi, Koryak, Krymchak, Kryts, Kubachi, Kumyk, Kurdish, Kyrgyz, Lak, Lezgi, Lingua Franca Nova, Macedonian, Mansi, Mari, Moksha, Moldovan, Mongolian, Montenegrin, Nanai, Nenets, Nganasan, Nivkh, Nogai, Old Church Slavonic, Oroch, Orok, Ossetian, Russian, Ruthenian, Rutul, Selkup, Serbian, Shor, Shughni, Slovio, Tabassaran, Tajik, Talysh, Tat, Tatar, Tindi, Tofa, Tsakhur, Tsez, Turkmen, Tuvan, Ubykh, Udi, Udmurt, Ukrainian, Ulch, Urum, Uyghur, Uzbek, Votic, Wakhi, West Polesian, Yaghnobi, Yakut, Yukaghir, Yupik
Information about the history of the Cyrillic alphabet
ALPHABETUM - a Unicode font specifically designed for ancient scripts, including classical & medieval Latin, ancient Greek, Etruscan, Oscan, Umbrian, Faliscan, Messapic, Picene, Iberian, Celtiberian, Gothic, Runic, Old & Middle English, Hebrew, Sanskrit, Old Nordic, Ogham, Kharosthi, Glagolitic, Old Cyrillic, Phoenician, Avestan, Ugaritic, Linear B, Anatolian scripts, Coptic, Cypriot, Brahmi, Old Persian cuneiform: http://guindo.pntic.mec.es/~jmag0042/alphabet.html