I save all scraps (I throw away selvedges) I am working on a spider web at the moment and this uses REAL crumbs. The other reason I save them is my Daughter, she will often ask for fabrics for collages or to fiddle and these bags of small scraps are ideal. (keeps her off my FQs!!)
I also attended a workshop recently where the tutor showed us that she saves scraps by colour and sits and snips them into tiny pieces in front of the TV - then she Irons bondaweb onto a piece of plain fabric and peels off the paper - she then sprinkles over her snipped fabric and irons until all the bondaweb is covered (I suppose you could use 505 for this too) then she free machine embroiders - kind of stipple - all over using a matching or contrasting thread. This 'NEW' fabric gets incorporated into her hangings and art quilts - I thought it was a neat idea....