I watch way too much TV. This summer, though, it's down to a minimum - Continuum and Dexter. It's Dex's final season, so yay for that.
Shows I used to watch that I don't anymore, though? If you mean current shows, I don't think I have any... I tend to stick with my shows to the bitter end, as long as I've seen more than three episodes to begin with.
Show list by genre:
Castle
Person of Interest
Homeland
Psych
Save Me (might be canceled, haven't heard)
Dexter
Hit & Miss (though it's been canceled; I've only seen the first two episodes)
Orange is the New Black (Netflix only; prison dramedy at a women's prison, with a "fish out of water" woman convicted 10 years after leaving the criminal world. Nominally based on reality.)
Lost Girl (Dexman's right.)
Arrow
Game of Thrones
Continuum
Supernatural
Nikita
Futurama
Dr Who
Through the Wormhole
How *** changed the world
Intermittently other shows
Shows killed before their time - Sarah Connor Chronicles, FireFly, Jeremiah, Dollhouse, and far too many others to count.