You don't need an Amazon Voucher, just click on the modules to download.
Modules:
Lesson 1: Introduction to Digital Photography
Lesson 2: Outdoor Lighting
Lesson 3: Indoor Lighting
Lesson 4: Landscapes
Lesson 5: Portraits
Lesson 6: Nature Photography
Lesson 7: Night Photography
Lesson 8: Street Photography
Lesson 9: Introduction to Editing
Lesson 10: Action and Sports Photography
Lesson 11: Pet Photography
Lesson 12: Trick Photography
Lesson 13: Self Portraits
Lesson 14: Architecture Photography
Lesson 15: Travel Photography
Lesson 16: Advanced Digital Editing
Lesson 17: Child and Infant Photography
Lesson 18: Abstract Photography
Lesson 19: Macro Photography
Lesson 20: Event Photography
http://www.inst.org/digital/ds_crs_mods.html