Vonage voip for Spain
 

I use Vonage here in the UK. Recently had an 'email shot' from them announcing they are now able to cover Spain. See here Vonage Spain VoIP | Cheap Phone Calls from Spain to the UK | Cheap International Calls from Spain to UK

I've been using it for 18 months with no problem.

To use Vonage you will need a broadband connection and a router.