If you are a VoIP user and a Firefox user, then you may see a lot of possibilities with this. A company called Zoep has released an extension for Firefox 1.5 that allows users to call other Zoep users. Also, if you like to call landline phones then you can do so by pre-paying for your calls. Another bright side to this extension is the ability to talk to people that use Jabber clients like Google Talk.
Download Zoep Firefox Extension
News Source: Digital Inspiration