I've known how to make this butterfly for ages, so I thought I should share it with you;)
I realized it is really hard to explain the way I fold, so if you don't understand, please say so, I'll try to help;)
You can use any kind of paper, provided that it's foldable and has a nice color on one or both sides;)
First, take a square piece of paper with the white side up.
Fold it in half and fold the sides to the fold in the middle. Lay flat.
Fold down the corners, but don't let them touch the folds you've just made.
Fold the sides, over the corners you've just folded, it should look like this.
Fold the piece in half over the length.
Fold the corners down. (The corners of the CLOSED side)
Now comes the tricky part, you have to follow all the folds you've made, and this should be the result.
Fold the side in the middle (yeah right) down for about half a cm.
It should look like this.
Take the flaps and fold them over the fold you've just made.
Make sure it lay flat.
Now your butterfly has wings.
Fold the piece in half. (mountainfold)
Another tricky part; take one wing and fold it upwards, it should look like this:
Turn it around and do the same with the other wing.
If you lay it down on the table, the wings and the body will be shaped like a W, \/\/, so the wings point slightly upwards.
Take the butterfly in your hand, and fold the "body" like this:
Lay flat, the part that you've just folded up.
The last thing, fold the flap that connects the ings down, like this:
And here's your brand new Butterfly:-D