MySpace members will be able to make calls using Skype's web-based voice-calling service and the calls will be placed through MySpace's existing instant messaging technology.
Members of Skype will be able to link their own MySpace profiles to their existing calling service.
The two companies have also linked up their technology to make it easier for members of only one network to join the other.
MySpace has more than 110m members with about 8m of them actively using its instant messaging service while Skype has 220m registered users.
Both companies are striving to expand membership amid growing competition and are working on the basis that their value to individual users increases as they attract more members.
As well as the free calling services, MySpace users will be able to choose from paid Skype services including voicemail and call forwarding to a regular landline or mobile phone.
MySpace users will be able to block unwanted calls by adjusting their profile settings to "private", allowing only people on their friends list to contact them through Skype.
A window on the computer screen will also notify users of an incoming call and allows them to accept or block the call as they choose.