For winter 2011, there is:
a) One daily direct service between Lisbon Sete Rios Bus Station (Metro - Jardim Zoologico) and Seville Estacion Plaza das Armas.
Dept Lisbon: 20:45
Arr Seville: 05:15 (next day)
b) There is a second direct service operating on Thursday, Friday, Saturdays and Sundays.
Dept Lisbon: 09:00
Arr Seville: 17:45
Both these service are operated by Alsa.es.
Timetable here: http://bit.ly/9JMgx6
Prices: € 35.00 one way - € 61.00 return.
It is also possible daily to get an EVA/Rede Expressos bus from Lisbon Sete Rios Bus Station (Metro - Jardim Zoologico) to Faro and then connect with one of the twice daily EVA/DAMAS buses from Faro to Seville.
Dept: (Lisbon Sete Rios Bus Station (Metro - Jardim Zoologico) 01:00
Arr: Faro Bus Station 04:50
Dept: Faro Bus Station: 09:20
Arr: Seville Estacion Plaza das Armas: 14:00
Dept: (Lisbon Sete Rios Bus Station (Metro - Jardim Zoologico) 10:30
Arr: Faro Bus Station 13:45
Dept: Faro Bus Station: 16:25
Arr: Seville Estacion Plaza das Armas: 21:15