Further to the above, I quite like the outdoor terrace at Changi, Singapore. Was there only yesterday
Outside of the UK, quite a few airports cater to the evil weed. From memory, I can remember the following (I have been to all of the below in the last couple of years, so can vouch for them).
Europe
All the German airports I've been to have the little cabins (Frankfurt, Munich, Dusseldorf). As do quite a few other European airports (Schipol, Warsaw, Prague to name 3). Unfortunately, Krakow doesn't (and I went there a lot last year!)
Middle East
Dubai has some nice, Winston sponsored smoking rooms airside, spread throughout the terminal.
The BA Lounge had one at Oman, but didn't see any outside of the lounge in departures.
I transferred through Doha and the dedicated Qatar transfer lounge had smoking rooms that were actually very pleasant.
CIS
Moscow (DME) has a dingy smoking area - but if you have access, the BA lounge has a (slightly) nicer one. The one thing I do like about DME is they have a dingy smoking room in the baggage collection area whilst you wait for the bags to appear on the belt! Further afield, there is a small cabin available to all at St Petersburg, Almaty (Kazakhstan) and Tblisi (Georgia).
Asia
In addition to Changi, Hong Kong and Bangkok also have smoking areas. I don't remember smoking areas in either Mumbai or Hyderabad. Couple that with India's way too frequent "dry days" makes India a "must-avoid" destination for those who love red wine and nicotine before departure...
USA
Little more bleak, here. Nothing in any of the NYC airports, Vegas, LA or San Francisco. A little while back I was pleasantly surprised to find a smoking area in Washington DC (Dulles), opposite the United lounge, but suspect that will have closed now.