Pension Vergara--
I was in Sevilla in August and would recommend the Pension Vergara located in the Barrio Santa Cruz, just a short walk from the Cathedral. The pension is listed in the Let's Go guide. It is in a historical building run by a family (including the family dog!) It's located in the old town Sevilla, near the cathedral, alcazar, park. It's very secure, they lock the door at night, just ring the bell, and the dad will answer the door and let you in. We easily walked to all the sights from there. We had a double room and I think we paid around 40Euros for two people.
Pension Vergara, C. Ximenez de Enciso at C. Meson del Moro. Ph. 954 21 56 68
Sevilla Youth Hostel - (Instalacion Juvenil de Sevilla) - You could also stay here, it's very cheap and nice, but it's a little off the beaten path. (17-20 Euros). From the old town, it was a 30 min walk or 15 min bus ride. It reminded me of a college dormitory, but it has air conditioning, a plus if you are going in the summer. Also had parking in front of the building.
Sevilla Hostel - C. Isaac Peral #2
Tel - 955 056 500 or 902 510 000
website -
www.inturjoven.com I'm not sure about this website, I haven't checked it out.
I hope this helps you!