SnapNames is a web domain name marketplace - meaning that they only deal specifically with domains that are currently owned by somebody else. They offer daily and premium auctions, private brokerage of domains, and buy-it-now listings for buying and selling domain names, including over 30 million domain names that aren't all, as you'll find on some services, exorbitant. They have over three million customers, including a significant number of small businesses, which is worth it.
GoDaddy — This extremely popular registrar (probably the biggest today) offers .com domain names for $9.99 (plus 20 cents) per year (or $6.99 plus 20 cents if you transfer from another registrar). They have a web interface to manage your domains, free web redirection (where people who visit your domain will get transferred to another web address of your choice), free starter web page, free parked page or free "for sale" page, and an optional private domain registration where your domain is registered in the name of a proxy company. Besides .com, they also sell .us, .biz, .info, .net, .org, .ws, .name, .tv, .co.uk, .me.uk and .org.uk, etc. Note that (as with all registrars) the exact price varies depending on which domain you are registering (for example some domain suffixes are more expensive than others). Both credit card and PayPal payments are accepted.
FatCow has one of the cheapest offers for an entire website package, with hosting and domain names for just thirty cents during your first month. After, that the price is $10.99 a month or $59.88 for the whole year, in a shared hosting package with enough bandwidth for most people. This is a limited promotion I found, but they still sell fairly well-priced packages (their "fat" options come with extras like marketing and advertising credits), and will gladly offer you perks for transferring your domains and hosting to them.
Now it’s time to see if your domain name choices are available. Once you’ve come up with a few strong domain candidates, it’s time to plug them into Namecheap’s domain name search bar. We will search available domain names for you and let you know if your first choice of second-level domain or TLD is available. We’ll also suggest some alternate TLDs you might try if your first domain choice isn’t available.