The following links are free online resources from the publishers of the books listed. They include listening files, as well as grammar, reading, listening, and pronunciation exercises.

Ventures Audio:
http://www.cambridge.org/us/esl/venturesadulted/venturesarcade/studentaudio/

Ventures Arcade:
http://www.cambridge.org/us/esl/venturesadulted/venturesarcade/

Touchstone Audio:
http://www.cambridge.org/us/esl/touchstone/audio/

Touchstone Arcade:
http://www.cambridge.org/us/esl/touchstone/student/index.html

Passages Audio:
http://www.cambridge.org/us/esl/passages3/audio/

World Class 2 Audio:
http://www.cengage.com/resource_uploads/static_resources/1133565891/50134/index.html