If you are looking for top level free .com, net, .org, .tv, .cc, .mobi, etc. domain name of your choice (eg. yourdomain.com), i recommend DDBoard. You have a total control over the domain you got from there. I got a couple of free domain names from them in just a month. You just need to be active on the forums by posting, playing arcade, etc. Check it out if you're interested...
http://www.ddboard.com

I hope this info becomes helpful esp. to those who doesnt have any way of paying a domain name (no paypal, no credit card, etc)