I love how many of them are now on Netflix/Hulu.
Favorites not/little mentioned include:
Rev. (the most honest, funniest look at faith in a long time)
The In-Betweeners (vulgar and very funny series about high school boys)
Fresh Meat (similar to I-B, but at university)
Peep Show (probably the most important British sitcom since The Office)
Foyle's War (gentle mystery series set during WWII)
Whites (about chefs--shame it only lasted for a season)
Extras (Ricky Gervais' second show, about, well, movie extras)
The Thick of It (highly vulgar and very funny political show)
The IT Crowd (started many of the best comedians of the past decade)
Life on Mars (they made a bad US remake)
Luther (too creepy for me, but my husband loves it)
Lewis (another mystery, sequel to Inspector Morse, set in Oxford)
I'd think of others, but I want to go rewatch some things...