you have to donate to ligitimate non=profits that offer 'tax-receipts' such as good will, womens resource center, salvation army, habitat for humanity ect...
my 'tax man' told me you can claim actual (cost) of the fabrics ... in order to use your donations for tax purposes you have to be very good about saving receipts...the receipt you receive from the non-profit; the actual purchase receipts so you can show how much you did pay for the fabric in the first place. same for donating quilts...you can only claim cost of materials, not what you think the quilt is worth.
my husband and i have between $2500 and $3500 in donation receipts every year so always get to use the deduction, but the IRS does look at these amounts and it can (red-flag) your return for an audit...if they think you are trying to (scam them) so make sure to save every receipt and be prepared to prove your claim.