Listmania!
ELT: Methodology: CELTA, TKT, ICELT
Learning and Teaching English: A Course for Teachers (Professional/Academic)Learning and Teaching English: A Course for Teachers (Professional/Academic) by Cora Lindsay
Buy new: £18.05 / Used from: £12.06
ISBN: 0194422771 Very comprehensive and designed with the TKT and CELTA in mind
Teaching Practice:  A guide for teachers in trainingTeaching Practice: A guide for teachers in training by Roger Gower
Buy new: £14.30 / Used from: £6.00
ISBN: 1405080043 Slightly expanded 2nd Edition. The 1st Edition 0435240897 is essentially identical excepting a detailed coverage of lexical rules. If this is of interest, read The Lexical Approach
A Practical Handbook of Language Teaching (ELT)A Practical Handbook of Language Teaching (ELT) by David Cross
Buy used from: £1.89
ISBN: 0133809579 Good but largely forgotten since it became lost in the Longman ELT list
The Practice of English Language Teaching (4th Edition) (With DVD) (Longman Handbooks for Language Teachers)The Practice of English Language Teaching (4th Edition) (With DVD) (Longman Handbooks for Language Teachers) by Jeremy Harmer
Buy new: £21.84 / Used from: £22.60
ISBN: 1405853115 Harmer's PELT 4th Edition with DVD. Older editions can be picked up for pennies (1) ISBN 0582746124 (2nd) ISBN 0582046564 (3rd) 0582403855
Teaching English as a Foreign Language (Teach Yourself Series)Teaching English as a Foreign Language (Teach Yourself Series) by David Riddell
Buy new: £5.97 / Used from: £4.00
ISBN: 0340868562 Ideal if your doing a 1 week uncertificated intro course but that's it!
Practical Techniques for Language Teaching (LTP teacher training)Practical Techniques for Language Teaching (LTP teacher training) by Michael Lewis
Buy new: £18.77 / Used from: £17.83
ISBN: 0906717558 Were I starting out in ELT and could buy just one book, this would be it. It's interesting how many authors have taken so many of its excellent ideas! Also under ISBN 9999463207
Source Book for Teaching English as a Foreign LanguageSource Book for Teaching English as a Foreign Language by Michael Lewis
Buy used from: £0.24
ISBN: 0435240609 A must have!
At the Chalkface: Practical Techniques in Language Teaching (ELT Methodology)At the Chalkface: Practical Techniques in Language Teaching (ELT Methodology)
Buy used from: £0.45
ISBN: 0175560285 Practical guide to theory & practice in ELT; articles on presentation, practice & production in conversation lessons, skills, vocabulary, skills. Same as ISBNs 071318177X & 071318504X
A Training Course for TEFLA Training Course for TEFL by Peter Hubbard
Buy new: £14.60 / Used from: £5.76
ISBN: 0194327108
The TKT CourseThe TKT Course by Mary Spratt
Buy new: £8.97 / Used from: £7.08
ISBN: 0521609925
Teach English Teacher's Workbook: A Training Course for Teachers (Cambridge Teacher Training and Development)Teach English Teacher's Workbook: A Training Course for Teachers (Cambridge Teacher Training and Development) by Adrian Doff
Buy new: £12.66 / Used from: £1.48
ISBN: 0521348633
Teaching English as a Foreign Language (ELT Methodology)Teaching English as a Foreign Language (ELT Methodology) by C. Dawson
Buy used from: £0.90
ISBN: 0174442009 An excellent short and very practical introduction. Also turns up under ISBN 0245539298
Teaching and Learning in the Language Classroom (Oxford Handbooks for Language Teachers)Teaching and Learning in the Language Classroom (Oxford Handbooks for Language Teachers) by Tricia Hedge
Buy new: £16.71 / Used from: £15.52
ISBN: 0194421724 Excellent and a clear challenge to Harmer's PELT which is really aimed at pre-service teacher trainees
Learning TeachingLearning Teaching by Jim Scrivener
Buy new: £15.08 / Used from: £12.41
ISBN: 1405013990
The English Teacher's Handbook: A Short Guide to English Language TeachingThe English Teacher's Handbook: A Short Guide to English Language Teaching by Ronald V. White
Buy new: £6.49 / Used from: £4.50
ISBN: 0952280817 An excellent short snappy introduction to ELT. Good if you're doing a 1 week intro course. Previous printings are ISBN: 0245539271 and 0174441843
Introduction to Teaching English (Oxford Basics)Introduction to Teaching English (Oxford Basics) by Jill Hadfield
Buy new: £14.00 / Used from: £8.18
ISBN: 0194419754 Looks like the Hadfield's have written another winner. A solid introduction for those new to TEFL
Language Teaching Methodology: Textbook for Teachers (Language Teaching Methodology Series)Language Teaching Methodology: Textbook for Teachers (Language Teaching Methodology Series) by David Nunan
Buy used from: £18.00
ISBN: 0135214696 Cerebral and fantastic. More suited for DELTA than CELTA
Learning to Teach English: A Practical Introduction for New TeachersLearning to Teach English: A Practical Introduction for New Teachers by Peter Watkins
Buy new: £13.19 / Used from: £15.00
ISBN: 1900783746 Great for new teachers preparing for the CELTA, TKT, Trinity or London TESOL teacher training qualifications
Teaching English as an International Language: From Practice to Principle (Language teaching methodology series)Teaching English as an International Language: From Practice to Principle (Language teaching methodology series) by Peter Strevens
Buy used from: £9.24
ISBN: 0080253334
The Teaching of English as an International Language: A Practical GuideThe Teaching of English as an International Language: A Practical Guide
Buy used from: £0.05
ISBN: 0175564973 Sold by the bucket by Nelson ELT overseas and can also be found in the orginal Collins ELT editions under ISBN 0003700208 (PB) and ISBN 0003700194 (HB)
How to Teach English: An Introduction to the Practice of English Language Teaching (2nd Edition) (With DVD) (How To Series)How to Teach English: An Introduction to the Practice of English Language Teaching (2nd Edition) (With DVD) (How To Series) by Jeremy Harmer
Buy new: £21.02 / Used from: £19.25
ISBN: 1405853093 2nd Edition with DVD. 1st edition 0582297966 can be picked up for pennies. However, you're better off getting 1405853115 which includes everything in this book and more
Teaching and Learning English: A Sourcebook for Teachers and Teacher-Trainers (Sangam ELT Series)Teaching and Learning English: A Sourcebook for Teachers and Teacher-Trainers (Sangam ELT Series) by M. L. Tickoo
Buy used from: £29.55
ISBN: 8125023070 Provides a surprisingly good introduction and overview!
A Course in Language Teaching: Practice and Theory: Trainee's Book (Cambridge Teacher Training & Development)A Course in Language Teaching: Practice and Theory: Trainee's Book (Cambridge Teacher Training & Development) by Penny Ur
Buy new: £5.88 / Used from: £3.51
ISBN: 0521656249 Superb! Rock solid - you're on an excellent TEFL course if they recommend this as your core trainee text
The English Language Teacher's Handbook - How to Teach Large Classes with Few Resources (VSO ELT)The English Language Teacher's Handbook - How to Teach Large Classes with Few Resources (VSO ELT) by Voluntary Service Overseas
Buy new: £8.89 / Used from: £2.74
ISBN: 0826447872 Excellent - and inexpensive!