It's been days since Co.CC has shut down and obviously, people have started looking for a better alternative. Here I have made a list of free domain registration services that can act as an alternative to Co.CC. All of the free domains suggested here are indexed by Google as of the moment of making this post. So, you don't need to worry about not ranking on search engine. But, we can't be sure what will happen at a later date. Facebook, however, could have blocked multiple of them.
DotTk provide free top level domains which belongs to the country Tokelau. They provide URL redirection service as well as DNS support for the domains. However, there is a special condition that your website must get at least 25 visits per 90 days in order to keep using the .tk domain. There are also lots of unfavorable reviews of .tk on the web. Users say that after you start getting lots of traffic, they get unreasonably strict regarding your site's content and then park your website at Sedo for their profit.
You can register up to 100 cu.cc domain names for free. They offer free DNS service with full MX, A, CNAME and SOA records as well. There is also an affiliate program in place through which you can make money by referring your friends. They have 24 hour abuse report response policy which is very good for a free domain service.tweet I received from the guys at Co.Vu, I was made aware of the site. Co.Vu seems to be a really simple subdomain provider. Just sign up with Facebook and you can have your own co.vu domains in literally 5 seconds. You can also directly set up your domain from Co.Vu's admin panel so that you can use it with Tumblr, Posterous, Blogger, Bit.ly, or Phpfog. However, you will need to upgrade to their pro plan if you wish to use NameServers with your co.vu domain. Free users are only allowed to modify DNS records - either Adress (A) record or Canonical Name (CNAME) record. They also have a referral program in place.
What earlier used to be CZ.CC has now reborn as Uni.me. You can register unlimited number of free domains with uni.me extension but be sure to use it on a ready made website since they automatically close your account if your site doesn't get visits for 10 days.
OthersHere is a list of other free sub domain providers. Go through their site to learn about them in detail. As mentioned earlier, only the ones that are indexed by Google are listed here. If you find any of the domains that are not indexed by Google, then please let us know.