The August issue of PC Pro magazine has a report all about VoIP including reviews of some IP phones such as this one
Just plug it into your router, configure for your VoIP provider and away you go.
Check out:
www.babble.net
www.btbroadbandvoice.com
www.call18866.co.uk
www.freeworlddialup.com
www.pipemedia.net/pipecall_pipecall.htm
www.sipgate.co.uk
www.skype.com
www.vonage.co.uk
And it's not just the telephone that's headed the IP way. Digital TV and Video on Demand over IP are already here in some places (eg.
http://www.homechoice.co.uk/) and I'm sure it wont be long before Amazon is looking after your album purchases for you and streaming them to your internet media player on demand.