I am not a big coffee drinker, but there is a Nespresso machine at work that I have been "stealing" the used pods from to experiment with. However, I have discovered there are genuine and non-genuine pods. Genuine pods are made of aluminium and come in different colours for different flavours. Non-genuine ones are plastic. Don't get me wrong, I can still use them for something, just not the same way as first planned.
Another brand of pod is the one we have at home, called Caffitaly. These pods are bigger, but also have two plastic pieces inside. They are easy to dismantle, and I have found that these "inserts" are very useful in their own right. I have used them for many other projects, like necks, or bases for things. They are a great addition to my bits and pieces box ;)
So, these are some types that I have had from the machine at work (they provide the machine, but you have to supply your own pods) There are probably more out there, but these are all the ones I have found, so far......
A- non-gen V1
B- non-gen V2 - the closest in shape and size to the genuine pod
C- genuine Nespresso pod
D- Caffitaly pod, with two different inserts taken out. One is in the base, one in the top
E- non-gen V3
F- non-gen V4
All are plastic, EXCEPT the genuine Nespresso pod, which is light aluminium. You can see how the machine pierces the in three points on the Nespresso, but the Caffitaly only has the one, in the point.
The other main difference I can see, is on the other side.
On the left is the Nespresso, the right is the Caffitaly. You can see the difference in size and production method of the two side by side. (Note that the Caffitaly one here has not been used to make a coffee...yet.)
It should be noted that coffee pods are very bad for the environment, so any chance to stop them going into landfill has got to be a bonus, although Nespresso do have recycling points around the place. http://www.nespresso.com/ecolaboration/au/en/recycling.html
They can be great for hats on small projects (I have used one for a snowman ornament) or bells, put two together with some rice inside for maracas or tops for lighthouses, or whatever else you can think of. You just have to think outside the box! :)