Checks Unlimited takes up to 70% off select checks via coupon code "9B5X". That's tied with our April mention and among the best discounts we've seen from Checks Unlimited in over a year.
A best bet is the Batman Checks (one box, pictured) for $21.99 before the coupon, $7.50 after. Even better, buy four boxes for $22.50 after discount ($5.63/box). With free shipping, that's $41 off and the lowest total price we could find.