If you want to see a great drama, I highly recommend that you grab Season 5 of The Shield off of iTunes or Netflix. All 6 of the seasons of the series are great and worth seeing (the 7th and final season is still to come), but I think that you can jump in at any point and watch. In my opinion, Season 5 is the best of the lot so far.
The Shield is a gritty cop drama about a squad in the Farmington neighborhood of Los Angeles. It focuses on a group of detectives known as the Strike Team led by Vic Mackey, a tough-ass detective with iffy morals played by Michael Chiklis. The Strike Team is a really effective group of cops who combat the big stuff in their low income, gang- and drug-infested neighborhood. They bend and break the rules (even the big ones, like murder) to get the big bad guys, often letting the little bad guys go, and sometimes skimming some cash and dope and weapons off the top. The series follows the Strike Team's day-to-day work, as well as the work of the other detectives and officers in the Barn, the converted church that serves as their squad. The ongoing story is always how IAB never seems to catch Mackey and his team in the act. They know he's a dirty cop, but they just can't seem to nail him on it. The subtext (ha ha) is my favorite kind: there are no good guys or bad guys. Everyone is somewhere in the middle. We can sympathize with Mackey, even though he is a killer, and manipulates his team to get what he wants. Even guys who are about as far from perfect as you can get can make a difference. There is hope for humanity.
I love this season because it guest stars Forest Whittaker as the totally obsessed IAB Lieutenant Jon Kavanaugh. Kavanaugh is driven crazy by his inability to catch and prosecute Mackey. He can't think about anything else, and actually loses perspective on his own moral code in the process. Also, his ex-wife is played by Gina Torres, and that fact alone is worth tuning in for.
Without spoiling too much, I will say that Kavanaugh and Mackey hate each other more than any two people I can think of. These two actors are so much fun to watch. This show is not for the delicate among us -- Sly B couldn't watch it without months of nightmares. If you can handle the blood and guts and realistic crime stuff, check it out. You won't be disappointed.