This one's apparently so new that it hasn't made the retailmenot site yet. :)
The link is
http://www.fabric.com
Get 15% off orders of $40 or more by using the code
BOXSTF42 at checkout. Expires 6/7/11. Excludes sewing and embroidery machines.
Don't forget you automatically get free shipping on orders over $35, so that'll save you even more money. :)
(no affiliation)