Some of the key books I've used for phonology over the years with my own, very subjective, comments

Baker, A. Introducing English Pronunciation. 1982. Longman.
Not a bad read.

Baker, A. Ship or Sheep. 1981. CUP
A classic and still helpful for students struggling with specific sounds. I find it helps them recognise the sounds they do not have in their own language and that students enjoy using the book for self study.

Baker, A. Tree or Three. 1982. CUP
Ditto the above which it follows.

Bowen, T & Marks, J. The Pronunciation Book. 1992. Longman.
An absolute must read. Definitely worth buying. Full of classroom ideas.

Brazil, D. et al Discourse intonation and language teaching. 1980. Longman.
Very interesting and goes well with the speaking input too. However, pretty heavy going and really only for those who want to go into this area in depth.

Cook, V. Using intonation. 1979 Longman.
Excellent, like almost everything by this author.

Gimson, A. An introduction to the pronunciation of English. 1980. Edward Arnold
Probably still the best introduction to the area.

Hubicka, O. Why bother about phonology? Practical English Teacher 1/1 1980.
A short article which still manages to cover most of the discussion points around the teaching of phonology.

Kenworthy, J. Teaching English pronunciation. 1987 Longman.
Another absolute must read and if you're going to buy a book on phonology make it this one. Very practical and full of classroom exercises that work.

MacCarthy, P. The Teaching of Pronunciation. 1978. CUP
Another author who never fails to write for teachers and not academics.

Mortimer, C. Elements of Pronunciation. 1984. CUP
Although republished fairly recently, it is still outdated. There are a few gems within, but I'm not sure it's worth wading through to find them.

Roach, P. English Phonetics and Phonology. 1983 CUP
The tour de force of phonology books. Too advanced for most Diploma courses and only worth going into if you want to go into phonology in real depth. A wonderful book. It's not practically classroom based.

Wells, J & Colson, G. Practical phonetics. 1971. Pitman.
Very usable like most books from Pitmans but not nearly as practical as they would have you believe.