TelCan callback
Excellent rates. Instant web billing, web trigger. RECOMMENDED!
* online signup
* FAQ 
* rates / leg rates
* contact telcan
* free phone call 
   to telcan support
* report problem
* trigger call
* customer login
* business
   opportunity,
   agent signup

US residents
* make cheap phone calls from inside the US

* Business Opportunity

net2phone
Call any phone anywhere in the world from your PC computer via internet. 10 cents to Britain, Germany from Asia, South America, Europe,anywhere!
*further explanations
*net2phone website
*rates
*download
*Business Opportunity

Phone card in all countries
*phone cards good for travellers

Traveltel
Prepaid Telephone card. Pay directly over the internet.  International ong distance phone access from any phone in  over 40 countries
*info
*Rates
*Registration

Phone card inside USA
*long distance phone cards
*dirt cheap calling cards 

More Callback Companies
I recommend Telcan callback and Access Authority further above, but maybe you want to compare or try these callback providers
*Kallback and Aquila signup,rates