Free Domains are offered by cz.cc with up to 5 free domains per account before you are required to upgrade to a VIP account.
Ease of use
The Interface is incredibly straight forward and once you have created an account it takes seconds to add or remove domains. The Who is function is straight forward and easy to use, it even suggests alternatives if your desired free domain name is already taken. Unfortunately the free domain service does not store your DNS settings so you have to enter them manually when you create new domains.
There are no major restrictions on the domains, you may use the domain in any way you see fit including redirects. The domain operates exactly like a traditional domain and once configured you will not notice a difference.
Indeed the domains are 100% free, there is no advertising or reciprocal linking required to use the service. No minimum traffic requirements are enforced either.
If you require more than 5 domains you will need to pay a fee, you may also pay a small fee if you require SSL for your domain. The donation or paid option is well priced and allows for 150 domains in total for a mere $9.99 which includes priority listing in the directory and a back link on the donation page. There are also certain domains which are reserved as premium domains and cost $4.99 per year however the reserved list is not excessive.
cz.cc is one of the best free domain services available with an incredibly easy to use interface and fantastic features. My only real complaint is having to add my DNS servers manually for each domain, if the service included the ability to save my DNS servers in my preferences it would be perfect.