There are a number of small but interesting events taking place in Aragon this month, a much overlooked region next to Catalonia, including the Teruel fair and festivals in Barbastro (Sept 4-8) and Albarracin (8-14).

Over in Catalonia, there are three days of festivities in the middle of the month in Graus (Sept 12-15), with the highlight being the Mojiganga satirical procession. The latter part of the month is dominated by the Festa de Santa Tecla in Tarragona, Catalonia, including Castellets (Sept 15-24)

Then there's the biggest festival in Barcelona, the Festa de la Mercè (Sept 22-25), a centuries-old celebration that includes fireworks, people on stilts and, of course, copious amounts of alcohol.

Complete List of Festivities in September:
First week: Festival in Cadaques
First week: Tarifa has its festival.
First two weeks of September: Teruel fair in Aragon.
1-8: Fiestas de la Vendimia. Valdepeñas (Ciudad Real). Grape-stomping festival, with the 8th being the most important date of the event.
3-6: Fiestas del Motín. Aranjuez (Madrid). Re-enactment of a local peasants' rebellion in 1808.
4-8: Barbastro fiestas.
4-8: Fiestas en Honor de María Santísima de la Sierra. Cabra (Córdoba).
4-9: Fiestas de Moros y Cristianos en honor de Nuestra Señora de las Virtudes. Villena (Alicante). Moors and Christians festival.
5-6: Fiestas del Santo Niño, Majaelrayo (Guadalajara).
6 and 9: Cascamorras in Baza and Guadix, Granada, a bizarre festival involving throwing paint and water at each other.
6: Fiesta de la Beata. Santa Margarita (Mallorca).
6-10. Fiestas de Moros y Cristianos. Caudete (Albacete) and L'Olleria (Valencia). Moors and Christians festival.
7-8: Fiestas de la Mare de Deu de la Salut. Algemesí (Valencia).
7-17: Festival in Albacete, a couple of hours west of Valencia and Alicante.
8: Fiesta de la Virgen de La Guía. Llanes (Asturias). Religous festival.
8: Ferias y Fiestas de La Consolación. Utrera (Sevilla).
8: Fiestas de Nuestra Señora del Pino. Villa de Teror (Las Palmas). Religous festival
8-9: Fiestas Patronales en Honor de la Virgen de Ermitana. Peñíscola (Castellón).
8-13: Entrada de toros y caballos Segorbe near Valencia. Taunting of bulls by men on horses.
8-14: festivities at Albarracin
Second week: Mijas, Andalusia, has its festival.
7-16: Film Festival of the Atlantic, Alcances in Cádiz.
Second week: Salamanca has its Fiesta de la Virgen de la Vega.
11-14: Romería de Nuestra Señora de la Barca. Muxía (La Coruña). Religious pilgrimage.
11-16: Jornadas de Guitarra guitar concerts in Denia, near Valencia.
12-15: Fiesta Mayor y Corre del Bou. Cardona (Barcelona). Bull run in the streets, concerts and dancing with people dressed as giants.
12-15: Fiestas Patronales del Santísimo Cristo y San Vicente Ferrer. Graus (Huesca).
13: Romería de Nuestra Señora de Chilla. Candeleda (Ávila). Religious pilgrimage.
13: Romería de Hontanares. Riaza (Segovia).Religious pilgrimage.
13: Romería de la Virgen de Gracia. San Lorenzo de El Escorial (Madrid). Religious pilgrimage.
14: Festejos Taurinos en el Mar. Candás (Asturias). Bull run on the beach.
15: Toro de la Vega. Tordesillas (Valladolid). A festival in which a bull is sacrificed in the streets of Tordesillas. The festival predates bullfighting as we know it today by a number of years.
15: Fiesta de la Vendimia, Ainzón, Zaragoza. The Campo de Borja wine region has its grape harvest festival, with plenty of grape stomping, starting around midday.
15-24: Festa de Santa Tecla in Tarragona, Catalonia, including Castellets (human castle building)
Mid-Sep until mid-Oct: Bienal de Flamenco, important flamenco festival in Seville. Festival is every two years, in even years. (2006, 2008, etc).
17-21: Real Feria y Fiesta de la Vendimia. La Palma del Condado, Huelva, Andalusia. One of the oldest grape harvest festivals in Spain.
18-20: San Mateo. Camarena de la Sierra, Teruel, Aragon.
19: (date may vary) Día de América in Asturias, Oviedo (Asturias). Celebration of the emmigrants who left Oviedo for the New World.
20: Romería del Santísimo Cristo del Caloco. El Espinar (Segovia).
21-30: San Sebastián International Film Festival in San Sebastián, surprisingly.
22-25: Festa de la Mercè, important festival in Barcelona.
20-26: Fiestas de la Vendimia Riojana. Logroño (La Rioja). Wine harvest festival. Yup, that means more grape stomping.
Late September: Noche en Blanco (Madrid) Saturday Night (around the 20th) sees a full night of free cultural activities around the city.
27: Romería en Honor de los Santos Mártires Cosme y Damián. Mieres (Asturias). Religious pilgrimage.
Last Sunday of the month: Día de Campóo. Reinosa (Cantabria).
Last week: Ubeda and Torremolinos, both in Andalusia, have their festivals.
Sep 30 - Oct 6: Film Festival of Albacete