The Wikipedia entry has a lot of information about Ballroom Dance in general.

Ballroom dance refers to a set of partner dances that can be danced socially or competitively. There are different styles of dance, including:

• International style ballroom
• International Standard: Slow Waltz, Tango, Viennese Waltz, Slow Foxtrot, Quickstep
  
• International Latin: Cha Cha Cha, Samba, Rumba, Paso Doble, Jive
  
• American style ballroom
• American Smooth: Waltz, Tango, Foxtrot, Viennese Waltz
  
• American Rhythm: Cha Cha, Rumba, East Coast Swing, Bolero, Mambo
  
• Club (social) and other dances:
• West Coast Swing, Salsa, Nightclub two step, Hustle, Merengue, Lindy Hop, Bachata, Argentine Tango, etc.
  

Wikipedia provides more information on International and American style ballroom dance tempo and duration of competition round.

See also: Dance competitions