Office Depot offers a UPS My Choice Premier 6-Month Membership for free. (Click through the banner at the bottom of the page to sign up and apply coupon code "BLKZZMOT5" if it doesn't automatically apply.) That's the second-best offer we've seen for this UPS membership. (We saw a 1-year membership for free in May.) Premier Membership gives all the benefits of free membership, as well as access to a two-hour confirmed delivery window. (A 6-month membership typically costs $20.)
Note: You don't have to enter your credit card information to complete registration, but it's still a good idea to turn off auto-renewal once you've signed up.