Years ago I saw a warning not to throw out scraps of fabrics for bird nests because fabric doesn't dry out fast enough. The idea was that after a rain, the nests remained damp too long and actually cause the baby birds to get sick. As I recall, it was a professional ornithologist who posted this in a similar thread on a quilting forum. Haven't been able to find confirmation of this problem when Googling, though, so I don't know if it has been discounted since then or if I am just not Googling in a way that will find that info.
On a different note, tiny scraps of fabric can be cut to make fusible pictures. A few years ago there were a couple of books out about how to do this. The author was on tv and demonstrated taking a pile of similar-colored-scraps and snipping them on to a fusible. In fact, I think that technique may have been called Snippet Sensations. (Later). Okay, I found the book on Amazon. Here is a link to it:
http://www.amazon.com/Snippet-Sensat.../dp/0873418034
I just unpacked an Accuquilt Go! and cut my first die shapes. I think I am going to cut my fabric pieces even larger than they specify so that I will have scraps big enough for a scrap quilt. Most of the pieces I have so far are too small even for a string quilt.