InstaPro.net has a great deal going on for domain name registration
Right now you can pick up a .com for only $3.99 if you pick up one of their other products, like private domain name registration.
It's a pretty good deal so if you are in the market for a cheap domain name registration I would definately start there.
If you have been considering a private registration on a .com or other popular domain style, then you can get the domain name and registration, "out the door" for about $16.00 which is less than some places charge for a standard domain registration.
You can also transfer your domain to InstaPro if you have it registered at another site like Network Solutions if you think that saving about $20-$30 per year on your domain renewal sounds like a good idea. Sounds like a good idea to me!