I use left over material from my quilts for the charity quilts I make, sometimes people who know I make charity quilts will also stop by with fabric and donate this towards the quilting. On occasion when I am asked what I am working on while at my craft or church groups, the next time I go in I will be given fabric to go towards that as well.
On the whole though I tend to make and donate more quilts that I have born the full cost for and look at this as being my gift to what ever cause.