This isn't comprhensive but a quick sample;
Out of the current crop of US shows, I mainly watch
House (something about a cranky cynic with a high dose of sarcasm really appeals)
Dexter (amazing, though I thought last season felt rushed near the end)
Burn Notice (got into it after reading an interview with Bruce Campbell, quite a fun show, a bit like McGuyver on speed)
Stargate Universe (Think its cancelled, and some eps were poor, but overall I thought it showed promise, and no one really makes space sci fi anymore so I take what I can get)
Others Ive loved recently,
The Wire
Arrested Development (there's always money in that bananastand, heard whisperings of a film in the works)
Battlestar Galactica (though the very end was a bit of a let down)
The Walking Dead (wasn't sure if this was a one off or not)
The Unit (Schmaltzy family bits aside this was actually a rather decent show)
Heroes (it was beginning to repeat itself but made for a fun hours viewing)
Mad Men (Stopped watching at season 2, but hoping they'll repeat 3 soon on the box)
24
This side of the pond Ive really enjoyed recently;
Merlin (biped's done a good write up of this series, production values are quite high and for an adulty/kids show theres a lot going on)
QI (as panel formats go this one is quite interesting)
Psychoville (a black comedy from the peeps behind League of Gentlemen, insane is all I can really say)
Hustle (occasionally the plots are a bit naff but in general its quite an entertaining little heist drama)
Top Gear (stopped being a 'car' show a long while back and is now, as they self describe, just three blokes 'cocking' around. About as edgy as the Beeb get these days (as they seem rather appologetic to everyone recently, I think they're worried about the licence fee review and the new government) but I think they allow it to get away with more because of all the commercial cash it brings in.
Come Fly with Me (A decent if slightly overdone mockumentary of life at an airport from the 'little britain' team)
As for classic TV I could be here for years, briefly
Spaced, Father Ted, Red Dwarf, Star Trek's (all seasons, yes even voyager to an extent, TNG was the one I grew up with so at a stretch Id say thats my favourite, tbh they got lazy scriptwise after roddenbury died), Blackadder, Dangermouse, The A-Team (in fact most action/cop/fun/american shows from the 80s) Seinfeld, Cheers, Fraiser, Diagnosis Murder, Early eps of Friends ('the ones' where they're still trying to define the characters) Cowboy Bebop, The Young ones, The Thick of It, Battlestar Gal(old series), Babylon 5, simpsons, futurama, etc.