There are various artists, called 'Boo' or BOO! :

An Alt Rock band from South Africa, a rap trio from Detroit and a Czech-Austrian alternative rock band Boo (without exclamation mark). Boo is also a ‘monky punk’ band from South-Africa. The album ‘Shooting Star’ is from the South-African band. Boo is also the alias of a promising young MC/producer from Moscow (Russia), who has so far made his name through guest appearance on a smash radio hit “Expensive Love” (“Dorogaya Lubov’”) also featuring Loc (fellow rapper of T.A. Inc. fame) & Batista of Band’Eros. Boo has produced various tracks for many upcoming artists (his work includes production for a critically acclaimed hit by Faces - “All I Want”), developing his style through some 5 years of work. Right now he is workin on a major untitled group mixtape and LP project, slated for realease in early June ‘07.

Boo! (SA)
Shooting Star (2002), Chameleon Publishing

Boo (CZ/A)
Discography:
- Boo (1999), Indies
- Listen (2002), Indies
Boo (CZ/A) are: singer/violinist/guitarist Christoph Pajer (Metamorphosis, Boo), cellist/singer Andrea Konstankiewicz[úartist] (Rale, Tara Fuki, Boo), bass guitarist/guitarist Josef Ostřanský (Dunaj, Pustit musíš, Rale, Boo) and drummer Pavel Koudelka (Dunaj, Pustit musíš, Boo).

BOO (J)
There is also another artist by the name of BOO from Tokyo, Japan. A former rapper with the group, The Soul Nuts, he became a solo artist in 1998 singing RnB instead. He has 3 albums, “BLAQUE & P.P.”, ” POST SOULMAN” and “POST SOULMAN 2”