Microsoft will be launching a VoIP service that will be for Messenger Live users. the VoIP is available for the following countries:

US

UK

Germany

France

Spain

Will be available next week:

Austria

Belgium

Finland

Iceland

Italy

Netherlands

For Israel residents, the service will be available this month

for more info:
http://www.theregister.co.uk/2006/05/09/microsoft_messenger_beta/