LOL, I thought you were asking about cheapest dot com. I think one of the cheapest places would be http://www.name.com. Not sure if their customer service is up to par though. You can register a .com for $6.00
Oh man, after reading this I feel bad for paying $10 for at least like 12 domains at Bluehost dot com. Yikes!
A list which I have posted many times... Note: * Some registrars required a coupon code to have price cut, all coupon code will display in red color. Mydomain.com Price: As low as $5.95, depends how many you want to purchase. Mydomain.com coupon code: htmli.info - 15% OFF of your entire order by using this coupon. # Valid on all service provided by mydomain.com and all TLD / cctld domain registration, transfer and renewals. Register.com Price: Free! ( You must have a valid credit card ) # One credit card one domain ONLY. $35/year renewals fee Netfirms.com Price: $5.95 ( $9.99 renewals fees ) # One customer are eligible to get maximum 5 domains on $5.95, no push function is available. Name.com Price: $5.99 ( .com .net .org ) # Valid on new domain registration only. Godaddy.com Price: $8.15 ( .com ) Coupon code: CJCDEAL32 Domain.com Price: $7.60 Coupon code: htmli.info # Price valid on new registration, renewals, and transfer. Lower rate if you register in bulk. Dynadot.com Price: $2.99 (.info) # Great if you plan to get a .info domain and they allow test domain too
You can choose either Name.com $5.99 for new reg & renewal $7.99 or Godaddy.com $7.15 with promo code.