1 Rome by HBO and BBC , S1 and S2 (Elegant British English and great language - basiced on Edward Gibben's original works)
2 The L Word, S1, S3, S4, S5, S6 (Sexy and hot, very humorous. Beautiful actress. A lot of social and cultural topics)
3 Prison Break, only S1 (S1 is the best)
4 Boston Legel (very useful to improve English)
Because you mentioned Friends and Sex and the city, so i guess you'll like The L Word.