Skype is a popular (too popular?) Voice over IP (VOIP) solution. It's primary use is cheap long distance calls, technical conferencing, and low cost conferencing. There are several similar alternatives.
Now, however, Skype is getting .... interesting.
They're offering users a 'unversal number' that can be reached by external phones (hmm. What does it do with fax calls?). Calls can go to voice mail or get routed to the Skype client (if it's connected). Cost is about $60/year for one number and voice mail, but I'd expect a variety of hidden fees also exist.
If they also provided programmable routing (route to my mobile phone, route to my home phone, etc) I'd have signed up already, but given their infrastructure it doesn't seem far fetched to expect routing in a future release.
SkypeIn provides an affordable, flexible alternative to costly mobile phone roaming charges with SkypeIn personal numbers. SkypeIn customers can receive inbound calls to their Skype client from ordinary fixed telephones or mobile phones while they travel worldwide, providing seamless interconnectivity without having to pay costly roaming charges. Skype Voicemail enables users to manage incoming voicemail messages, making their Skype usage more ubiquitous...All Skype services are pre-paid, apparently they lead the industry in credit card fraud.
... SkypeIn customers choose a country and area code and are assigned a regular telephone number... Users may purchase up to three numbers from their home country in Denmark, Finland, France, Hong Kong, Sweden, the United Kingdom and the United States during the beta period.
Skype Voicemail customers can receive a voicemail message up to 10 minutes long from any user or traditional phone. Skype Voicemail customers may record their own personalized voicemail greeting, playback their messages, even while offline, and send incoming calls to voicemail if they away, offline or simply busy on another call.
SkypeIn and Skype Voicemail complement Skype’s first premium service, SkypeOut, which allows global calling to public telephone numbers for local rates....