NameBright is currently running a promotion for new .com registrations. The price is $6.29/year for pre-funded accounts and $6.59 for credit card payments, which is what I chose. Like many other domain registrars, NameBright offers free domain privacy on all .com registrations.
There is no promo / discount code required to take advantage of the discount, and it does not look like there are any limits to the number of domain names that can be registered. This promotion only applies to new registrations and not transfers or renewals.
I am unsure when this promotion ends.