Making a poncho can be a lot simpler than this, square piece of material, cut hole in middle, job done (see this for an example http://sewing.about.com/library/weekly/aa072904a.htm
If you want to go for the versatile, double layered design feature you'll need:
Towelling material (maybe old bath towels, tea towels, bath robes would fit the bill)
A warm layer (old fleece jackets, throws, blankets etc).
The larger the pieces of both you have, the less time and faffing needed!
Sewing machine, pins, scissors, thread, and fasteners (to join the two layers together): I used large poppers/ press studs.