Writing Academic English, by Alice Oshima and Ann Hogue, provides practical techniques for students planning to attend community college or university. I think the latest version is the fourth. I've used it in several programs with considerable success.
In Focus: Strategies for Academic Writers by Myra
Ann Shulman, however, is my current choice for intermediate ESL students.
The clear, detailed exercises allow students to learn academic writing
by actually writing short, focused pieces.
Finally, for advanced ESL students and international graduate students, I strongly recommend Academic Writing for Graduate Students, 2d ed.: Essential Tasks and Skills (Michigan Series in English for Academic & Professional Purposes) by John M. Swales and Christine A. Beer Feak. I teach two courses using this textbook at USC, and students make clear, significant progress by completing bite-sized writing exercises and analyzing short journal readings. The teacher's guide, called Commentary for, also deserves to be on your list.
Any Longman Dictionary – For whatever reason, Longman dictionaries seem much more accessible and practical in their design than other series. I’m particularly impressed with their Business Dictionary for English Language Learners.