I have found this registrar to have cheap prices - $ 6.99 only for domain registrations, and I registered with them several domains.
You can visit the site at www.nicbg.com

That's the cheapest I've ever seen. Not sure if they're reliable as I've never heard of them before.

Personally, I've always liked GoDaddy.com (long before the superbowl commercial) because they have great service/control and their prices are only slightly higher than that $6.99.

Hahaha that was some superbowl commercial godaddy had.