The best domain name price we could find with Netfirms was $7.99 USD for a .com domain name for the first year. (The second year returns to the regular price for Netfirms which is $9.95 per year per domain name.)
There are a few nice things about Netfirms that caught our eye:

Although they’re not the cheapest, [...]

GoDaddy currently has a special rate of $1.99 for any domain (.com, .us, .mobi, .biz, .net, or .me) but you need to read the fine print carefully:

The special rate of $1.99 per domain name per year only lasts for the first year. After that, the price goes back to $10.69 per domain per year [...]

We use Bluehost to host our websites. We used to love them, but they’ve changed their domain name privacy registration policy and so now we’re looking elsewhere to buy our domain names.
Bluehost used to charge $10 per domain name per year, which is a tad on the pricey side, but it came with free Domain [...]

Update (Dec 2009): www.cheap-domainregistration.com still offers their sale on .info domain names: $1.99 per domain name for the first year before eventually returning to the regular price of  $7.39 per domain name per year. They still offer $7.99 per .com domain name per year which is impressive since these guys are a Wild West (Go Daddy) [...]

Update (Dec 2009): DomainsAreFree.com still offers a sale price on .com, .org and .net domains:  $3.99 per domain name for the first year before returning to the regular price of $14.95 per domain name per year. Domain privacy is now listed as $8.99 per domain name per year. There are domain registrars that offer cheaper [...]