I found a quick way to hook your psp into skype using Furikup.
http://www.nch.com.au/pbx/index.htmlIt's a virtual PBX in itself, but there's a related program also released by them which is a SIP->Skype adapter which allows you to add skype as an external line to the pbx system, and allows you to route calls through it. There's setup instructions with it for setting up the uplink. BTW, this allows both receiving and making skype calls via ANY sip device, including the psp.
I was having some compatibility problems though, you'll see them if you set this up.
PS:: I have a SOCOM headset and was wondering if anyone has actually tested it with furikup...I was unable to get the mic to take input.