I just got Skype equipment for my PSP today.
I just got a Microphone-Headphone set for my PSP today. First you connect to a wireless internet connection and login to a Skype account. Well, first you have to make one. And then you can call people straight from the PSP. It's pretty sweet.
If I didn't explain it very well, then you go buy a PSP and then buy a Skype thing.
If you don't have Skype on your PSP, you are going to have to do a PSP Version update. Just ask me if you have no clue what the heck I'm talking about.