Try and visit the Barbican Centre in the city if you have time, they put stuff on like art exhibitions etc. and it's a very peaceful place.
Also the Charing Cross Road for Foyles bookstore and various side streets off it like Cecil Court for interesting bookshops. Soho has a few record stores as does Camden. Try the Music and Video Exchanges that are dotted around.
[Edited by sabbathfan at 20:27 on 25/09/10]