Source: snapvoip.blogspot.com

Since the official confirmation that Skype is coming to PSP, the slim only, team N00bz have released the beta Furikup, a free homebrew open standard alternative to proprietary Skype that works on both the PSP Slim and regular PSP, or Phat PSP units.
Here are some of Furikup’s best features according to Noobz.eu:(Noobs got hammered I think now off line.)

It’s free software - in both the beer, and speech senses.
You can use it anywhere in the world, subject to signing-up to a suitable local SIP-based voice-over-IP provider and being near a usable wifi access point. In many countries, you can find those for free or nearly-free - e.g. with SIPGate, in the UK, you can call to your PSP from any standard phone (landline or cellphone) for just the standard local call cost, and from PSP to another SIP phone (another PSP or a PC) for free.
It runs on both slim and fat PSPs.
It uses open standards, for maximum compatibility with other phone systems.
You can use a Go!Cam (Chotto Shot), Talkman microphone, or SOCOM-style headset for audio input. (And even if you don’t have any of those, you can still send audio from a WAV file in a pinch).
It’s still pretty much beta software - the audio quality needs some work (but it is usable), the UI isn’t very pretty, and video calls aren’t working (yet!). But it works, and it’s a nice demo of what is possible.

Since this is open source homebrew software, there are endless possibilities as to what inventive minds could do with this engine. We’d like to see a much nicer GUI (we suck at UIs!), and maybe a custom firmware plugin to use the engine as a teamspeak-style add-on feature for online games. Go on, go crazy and show us what you can do with it - you have our blessing!

They also note that the application contains code from the following projects:

• oRTP library by Simon Morlat and Lovadina Nicola
• oSIP and eXoSIP libraries by Aymeric Moizard

To download furikup0.1.zip (provided by exophase.com) untill N00BZ comes online.