Recommendations for good cable series?

OK, so I have a crazy schedule and can never watch normal primetime shows on TV. Lately I have been watching HBO, Showtime series on DVD through Netflix, rather than sit through 2 hr movies. I have watched and the City, The Sopranos, Six Feet Under, Queer as Folk. I need a new show to watch now. Any recommendations, cable or network? I am open to all suggestions but I like shows that are older and have a lot of DVDS I can watch in order, rather than having to wait for each new season.