IELTS Writing: IELTS 5-6+ (B1+) (Collins English for IELTS) by 
IELTS advantage. Writing skills : [a step-by-step guide to a high IELTS writing score] / Richard Brown, Lewis Richards.
Ielts Finesse by 
IELTS Washback in Context by 
Writing skills / Sam McCarter, Norman Whitby.
404 essential tests for IELTS. Academic module / by Donna Scovell, Vickie Pastellas & Max Knobel.
Focusing on IELTS : general training practice tests / Michael Clutterbuck and Philip Gould
Kaplan IELTS by 
Barron's IELTS with Audio CDs, 3rd Edition by 
Complete IELTS Bands 4-5 Class Audio CDs (2) by 
IELTS foundation : study skills : a self-study course for all academic modules / Jane Short ...
Find the answers to all your writing conundrums in Grammarly's handy grammar guide.
Grammarly makes sure everything you type is easy to read, effective, and mistake-free.
Check your text now with this automated proofreader and plagiarism checker.
Read the Grammarly blog here.
How long is the Writing paper?
What will I need to write about?
How is the Writing paper assessed?
[The above information is taken from The Official Cambridge Guide to IELTS Student's Books by Jakeman, V., Cullen, P. and French, A.]
Official IELTS Band Descriptors for Task 1 and Task 2, broken down into 'Task achievement', 'Coherence and cohesion', 'Lexical resource' and 'Grammatical range and accuracy'.
Writing for a purpose - from the British Council
IELTS Writing from Exam English
IELTS Writing help via YouTube: Explore the different videos available.
OWL Purdue Online Writing Lab: APA This link opens in a new window
From Purdue University, this guide gives a good introduction to referencing in the APA style.
IELTS writing tests from the Hong Kong Polytechnic University
Free IELTS Lesson - Academic Writing Test Task 2
From IELTShelpnow - gives useful tips to help you prepare
Free IELTS Lesson - Academic Writing Test Task 1
From IELTShelpnow - gives useful tips to help you prepare
Academic Learning Cafe - Quizzes This link opens in a new window
Grammar, spelling, vocabulary and writing quizzes
WriteFix This link opens in a new window
Aimed at people learning English and preparing for the IELTS exam - focusing on writing and speaking.
IELTS Preparation - Holmesglen Institute of TAFE
An in-depth look at tasks 1 and 2 in the IELTS writing test.
IELTS Online Practice Materials This link opens in a new window
From Hong Kong Polytechnic - listening, reading, speaking, writing
Parapal - English language exercises This link opens in a new window
Free online English lessons to improve your listening, writing, reading, vocabulary and grammar skills.