I recently came across this free domain service co.cc. It appears too good to be true! And it is. Unless your website does not rely on organic search traffic from Google, then you will be okay. Google is not indexing any site under the co.cc domain! Searching for site:co.cc on Google gives you nothing.
Back then, it appeared Google did pull all the co.cc form its index, see http://www.theregister.co.uk/2011/07/06/google_cans_11m_dot_co_dot_cc_sites/
But it appeared co.cc sub-domain sites have reappeared on Google.