Sony has partnered with eBay's Skype division and developed a portable version on the VoIP service for the PSP, effectively turning the gaming handheld into a Skype phone -- with the same functionality, as well its limitations.
Here's what we know:
In about 1-2 months, owners of the newer PSP model (the P-2000) will be able to download a firmware update and secure a free application that will allow users to make free PSP-to-PSP and PSP-to-PC calls so long as both parties are in a WiFi hotspot. PSP owners with the Skype firmware update can also make calls to conventional land lines (or cell phones) off the Skype network, however, a per-call charge will be assessed.
http://www.cnn.com/2008/TECH/01/08/psp.skype/index.html