It's a phone on a USB stick, it looks just like any USB memory stick, and it has (at last!) shipped into the UK. It's the Vonage V-phone.

But there is no sign of any good news for Mac or Linux users. You still need a Microsoft PC. And ,of course, being a SIP-based service it's not free: it costs £7.99 a month. So you might like to try experimenting with loading your Skype details into the V-phone's 250 meg memory chip...