Tenses

Take a look at this review of tenses (use and examples)
http://www.learn-english-today.com/lessons/lesson_contents/verbs/verb_tense-revision.html

You can choose whether to do exercises online or print them out. You can also read explanations on the uses of tenses.
http://perso.wanadoo.es/autoenglish/freeexercises.htm#TENSES

Common mistakes

Find explanations concerning common mistakes, do exercises and check your answers
https://docs.google.com/open?id=0B04H2T1abW4HZzFRMG9hVnVBaGs

The environment

Vocabulary and expressions to talk about environmental issues

https://docs.google.com/open?id=0B04H2T1abW4Hb1NQZjZiZzdZclU

Listening exercises

Here you can find the audio for your workbook

http://docs.google.com/open?id=0B04H2T1abW4HTEV2Z1lxUlZGZ0k