DVC membership allows you to take advantage of discounts for cash stays at DVC resorts booked through member services, usually 25%, but the discount isn't available all the time. I don't know of any non-DVC resort cash discounts simply for being a DVC member.
There are usually better deals available to the general public or for being an annual passholder, even for stays at DVC resorts. Right now the general public can get 30-40% off stays at DVC resorts where the normal DVC member cash discount is only 25%.