There are a number of music festivals taking place throughout Spain during the summer months. Here is a summary (adapted from a listing given by 20 minutos of some of the main ones:

Festival Name: Sonar
Genre:Independent Music
Location: Barcelona
Dates: 16th - 18th June
Bands: The Chemical Brothers Ellen Allien, Ada, James Murphy, Mu, Jeff Mills, Laurent Garnier, Cut Chemist, The Soft Pink Truth, Roisin Murphy, Afra, Noa 23, LCD Soundsystem, Le Tigre, Soulwax, Hood, Delasoul, Mouse on Mars, Khonno, FS Blumm...
Link: http://www.sonar.es/

Festival Name: Pirineos sur
Genre: World Music
Location: Lanuza (Sallent de Gállego, Huesca)
Dates: 8th - 30th July
Bands: Carlinhos Brown, Bebo Valdés, Joe Zawinul Syndicate, Madredeus y José Mercé, Lhasa, Ray Lema, Chico César, Astrid Hadad, Los Lobos, Mantequilla, Joe Zawinul & The Zawinul Syndicate...
Link: http://www.pirineos.sur.com/

Festival Name: Benicassim
Genre: Independent Music
Location: Benicassim (Castellón)
Dates: 4th - 7th August
Bands: The Cure, Oasis, Nick Cave, Keane, LCD Soundsystem, Underworld, Basement Jaxx, The Kills, Kasabian, Yo La Tengo, Dinosaur Jr., Fischerspooner, Kings of Convenience, Deluxe, La Habitación Roja, Xiu Xiu, ...
Link: http://www.festival-benicassim.com/

Festival Name: Mediatic Festival
Location: Alicante
Dates: 8th - 10th July
Bands: Amaral, Santiago & Luis Auserón, Bebe, Bunbury, Orishas, Pereza, Luz Casal o Los Ronaldos
Link: http://www.mediaticfestival.com/

Festival Name: Festival de Jazz de Vitoria
Genre: Jazz
Location: Vitoria
Dates: 12 - 16th July
Bands: Chick Corea & Touchstone, Koko Taylor y Us3 and others
Link: http://www.jazzvitoria.com/

Festival Name: Creamfields Andalucía
Genre: Various
Location: 13th August
Dates: la playa de Villaricos (Almería)
Bands: The Chemical Brothers, Felix da Housecat, Ladytron, Saint Etienne, 2Many Dj´s, Godfrapp + others
Link: http://www.creamfields-andalucia.com/

Festival Name: Festival de Jazz de San Javier
Genre: Jazz
Location: San Javier
Dates: 29th June - 30th July
Bands: Pat Metheny, Marcus Miller y John Pizzarelli + others
Link: http://www.jazz.sanjavier.es

Festival Name: Santander Summer Festival
Genre: Various
Location: Rostrio (Santander)
Dates: 8th - 9th July
Bands: The Chemical Brothers, Morcheeba, Los Planetas, Ocean Colour Scene, 2Many Dj´s, The Faint
Link: http://www.santandersummerfestival.com

Festival Name: ContemPOPranea
Genre: Various
Location: Alburquerque (Badajoz)
Dates: 29th - 30th July
Bands: Fangoria, La Habitación Roja, Astrud, The Sunday Drivers, Mercromina, Cooper o Australian Blonde
Link: http://www.contempopranea.com

Festival Name: Lorcarock
Genre: Rock
Location: Lorca (Murcia)
Dates: 18th June
Bands: Iron Maiden, Dream Theater o Stryper
Link: http://www.lorcarockfestival.com

Festival Name: Sonorama
Genre: Various
Location: Aranda de Duero (Burgos)
Dates: 19th - 20th August
Bands: Supergrass, !!!, Ash, Los Planetas, Mercromina, Astrud o Maga
Link: http://www.sonorama-aranda.com

Festival Name: Ortigueira
Genre: Celtic
Location: Ortigueira (A Coruña)
Dates: 7th - 10th July
Bands: Variety of Certic bands from around the world
Link: http://www.festivaldeortigueira.com

Festival Name: Azkena Rock
Genre: Rock
Location: Vitoria
Dates: 2nd - 3rd September
Bands: Queens of the Stone Age, Social Distorsion, Wilco, Monster Magnet, Bad Religion
Link: http://www.azkenarockfestival.com

Regards
Robbieroy