Some major calligraphic styles: Naskh, Thuluth, Muhaqqaq, Nasta'liq, Riqa'

Source:  http://www.sakkal.com/Arab_Calligraphy_Art7.html
(downloaded Dec. 1999)

Some of the most important calligraphic styles. Designed by Mamoun Sakkal, 1993. He offers many other designs on his homepage, including a special section devoted to modern calligraphy: http://www.sakkal.com/CalligContents.html