Call to landlines for free (selected countries only, see list below) voipstunt.com/en/index.html but note:
(I have however made calls that lastet more than 1 minute)
Argentina
Australia
Austria
Belgium
Canada
Chile
China
Croatia
Cyprus
Denmark
Finland
France
Germany
Gibraltar
Hong Kong
Hungary
Iceland
Ireland
Italy
Japan
Liechtenstein
Luxembourg
Malaysia
Monaco
Netherlands
New Zealand
Norway
Poland
Portugal
Singapore
South Korea
Spain
Sweden
Switzerland
Taiwan
United Kingdom
United States