For St. Patrick's Day, Samhain Publishing are offering 30% off with the coupon code
STPATTY12 until midnight EST when you buy
directly from their webstore (MultiFormat, DRM-free). If I typed the code wrong, there's a big banner on their front page to remind you.
There doesn't seem to be a minimum purchase amount and their coupon discounts have previously stacked on top of the 30% off new release/pre-order discount as well.
I'd advise loading up your cart with everything you think you want before checkout, as from previous experience, these things seem to be 1-use only.