the wire - possibly the (second) greatest tv series out there. set in and about the city of baltimore, pretty slow to pick up, but mezmerising. really really good. 5 series, complete
the prisoner - the greatest television series ever made. made in the 1960's, an intense spy thriller that delves deep into mind fuckery.
those are the two I really recommend, but if you like comedy or alternitive stuff I can also highly recommend;
father ted (comedy about 3 pariochial irish priests set on remote island)
garth meriangis dark place (strange hospital comedy filmed in style of 70's drama/horror)
police squad! original 80's naked gun tv series. only 6 episodes, but really good stuff. surreal.
well, thats all I can think of off the top of my head, the ones I would really recommed anyways.