I recently stumbled upon
http://www.telereduc.com/en/, which is a call-through service based in France with a range of numbers beginning 0811, 0820, 0826 and 0821.
To cut a long story short, while most of their numbers cannot be reached (at least from Sky Talk and Voxbeam), their 0821 338 009 number can be called for free via Sky Talk and can be used to call quite a range of destinations, at least according to the web site.
Evidence that the call is free from Sky Talk:
15/01/11 06:55:16 France (Including Corsica) 0033821338009 International Calls 00:00:59 £0.000
15/01/11 07:01:08 France (Including Corsica) 0033821338009 International Calls 00:00:51 £0.000
15/01/11 07:06:14 France (Including Corsica) 0033821338009 International Calls 00:00:50 £0.000
15/01/11 07:42:59 France (Including Corsica) 0033821338009 International Calls 00:00:53 £0.000
And the list of destinations they claim the number can be used to call:
Albania
Albania - Tirana
Algeria
Algeria - Algiers
Algeria - Oran
Algeria Assilabox
Algeria CAT
Andorra
Australia PRS
Australia Toll Free
Austria
Austria - Mobile - Connect
Austria - Mobile - MOBILKOM
Austria - Mobile - Other
Austria - Mobile - T MOBILE
Austria - Mobile - Telering
Austria - Salzburg NP
Bahrain - Mobile
Bangladesh
Bangladesh - Chittagong
Bangladesh - Dhaka
Bangladesh - Mobile
Bangladesh - Sylhet
Bermuda
Bolivia - La Paz
Brazil
Brazil - Belem
Brazil - Campinas
Brunei
Brunei - Mobile
Bulgaria
Bulgaria - Sofia
Bulgaria-Mobile-Mobikom
Burundi
Cambodia
Cambodia - Mobile
Cambodia - Phnom Penh
Cayman Islands
Chile
Chile - Easter Island
Chile - Mobile
Colombia
Colombia - Manizales
Costa Rica
Costa Rica - Mobile
Cyprus - Mobile
Cyprus North
Czech Republic
Dominican Republic
Egypt
Egypt - Alexandria
Egypt - Cairo
Egypt - Mobile
Finland
Finland - Helsinki
France - 810
France - Mobile - Bouygues
France - Mobile - Orange
France - Mobile - Other
France - Mobile - SFR
Georgia
Georgia - Tbilisi
Germany - Mobile - D1 TMOBILE
Germany - Mobile - D2 VODAPHONE
Germany - Mobile - E2 O2
Gibraltar
Greece - Mobile - Infoquest
Indonesia
Indonesia - Bandung
Indonesia - Mobile
Indonesia - Surabaya
Iran
Iran
Iran - Isfahan
Iran - Isfahan
Iran - Mobile
Iran - Tehran
Iraq
Iraq - Baghdad
Jamaica
Japan - Tokyo
Kazakhstan
Korea South - Mobile
Kuwait
Laos
Latvia
Latvia - Riga
Lebanon
Lebanon - Beirut
Liechtenstein
Lithuania
Macau
Macau - Mobile
Malaysia - Mobile
Mali - Bamako
Mauritius Mobile
Mayotte
Mexico
Mexico - Aguascalientes
Mexico - Puebla
Monaco
Mongolia
Mozambique
Namibia
Nepal - Kathmandu
New Caledonia
Panama
Paraguay
Paraguay - Asuncion
Paraguay - Mobile
Peru
Peru - Lima
Russia
Russia - Mobile
Russia - Outer Moscow
Russia - Overlay
Samoa US
San Marino
Slovakia
Slovakia - Bratislava
South Africa
South Africa - Cape Town
South Africa - Johannesburg
Swaziland
Sweden - Mobile - Comviq
Sweden - Mobile - Other
Sweden - Mobile - Telia
Sweden - Mobile - Vodafone
Syria
Taiwan - Mobile
Thailand - Mobile
Trinidad & Tobago
Turkey - Mobile - Aria
Turkey - Mobile - Aria
Turkey - Mobile - Ay
Turkey - Mobile - Ay
Turkey - Mobile - Other
Turkey - Mobile - Telsim
Turkey - Mobile - Turkcell
Turkey - Mobile - Turkcell
UK - Mobile - H3G
UK - Mobile - O2
UK - Mobile - TMobile
UK - Mobile - Virgin NP
UK - Mobile - Vodafone
Ukraine
Ukraine - Kiev
Ukraine - Lviv
Ukraine - Mobile
Ukraine - Odessa
Uruguay
Uruguay - Montevideo
USA - Alaska
Uzbekistan
Venezuela - Mobile
Vietnam
Vietnam - Ho Chi Minh City
Vietnam - Mobile
Zambia
To place a call, just dial the number you wish to reach after the initial announcement "Hello, welcome to Telereduc", followed by hash. It will repeat the number back to you and ask you to press 1 to confirm.
Dave