At any given time there is always some sort of fiesta going on in Spain. This guide should point you in the direction of some of the events in this area.
January
February
Fiestas de Carnaval - Águilas - 26/01/2008 to 09/02/2008
March
Día de la Vieja - Old Lady Day - many places on the Thursday in the middle of lent
April
Semana Santa - Holy Week - everywhere
May
June
Moros y Cristianos - Mojácar - 8/9/10 June 2007 - also other places on different dates
July
August
Creamfields Andalucía - Villaricos - more info
Feria de Almería - Almería city - 18th to 27th August 2007
September
October
November
Feria y Fiestas de los Santos - Albox - 1st to 7th November 2007
December
Medieval Market - Huercal-Overa - 21st to 23rd December 2007