I taught IELTS for two years in Nanjing. All of my materials came from this site--

<a href="http://www.cambridgeenglish.org/exams-and-qualifications/ielts/">http://www.cambridgeenglish.org/exams-and-qualifications/ielts/</a>;

These people created the test so i think its safe to say they would have the best study materials. Good Luck:)

thank you so much, Chelsea C.