Best free calling sites in the world. these are not unlimited however they gives some free minutes.
1. http://talkster.com
2. http://rebtel.com
3. http://spoofcard.com
4. http://voipraider.com
5. http://icall.com
6. http://freeipcall.com
7. http://evaphone.com
8. http://m.ibibo.com
9. http://m.mig33.com
10. http://m.talki.me
11. http://minowireless.com