Seville is full of joy and Sevillians' are a crowed that likes to party.
In the summer, when the temperature is still in the 30s at night, there's a big bar scene along the river, on Calle Betis in Triana and Arjona and Torneo on the other side, as well as outdoor bars in some of the parks. Clubbing moves to the Isla de la Cartuja, where young people pack the many seasonal outdoor venues. A Cubano (double measure of spirit with mixer) will normally set you back between 4 and 5 euros, while a small glass of beer (Caña) is about 1,20 euro. Red wine (Tinto) is reliable, often Rioja, and costs about 1.50 to 2 euros a glass, while the white (Blanco) is usually sweet and not to English taste.
Seville is great for going out due to the huge variety of venues in a small area. You can easily visit four or five completely different bars without walking more than ten minutes between any of them. The main areas are: Alfalfa, where Pérez Galdós gets so packed with people on Friday and Saturday nights that cars can't drive down it; Alameda, which has a more alternative scene, with lots of gay bars and clubs; and Calle Betis by the river in Triana, which is wall-to-wall with venues, from quiet bars to all-night clubs.
For a complete overview check out Oasis Sevilla Map