You don't need anything - two PSPs can create an 'ad hoc' connection with each other, with their own wireless capabilities. There is no need for any kind of add-on or cable, and so those do not exist.
I think you do. I'm not sure
PSPs connect to your wireless router. There's no additional cost for this, but you do of course need wireless internet.
Not at all, PSPs can connect to the PSN to download games without needing to modify the PSP.
PSPs are not like phones, with their internet packages and data transfer plans. PSPs connect to your wireless router in the same way as a laptop or PC does. So the internet doesn't 'cost' anything when you do this, but you do of course need to actually have wireless internet in the first place, and the PSP can only connect when it is within range.
you need infrared adapter...
The Sony DVP-SR200P would need an adapter to directly connect to an Ipod.
You'll need a mini-USB to USB connector to hook up your Sony camcorder to your PC.
No, you'd use a USB cable.
Because they use batteries.
Connect the Audio Out of the Sony set (Left + Right RCA) to the audio input of the X600 (1/8" stereo). You will need an adapter y-cable.
You need a VGA to RCA. You can buy these on eBay or other online sites.
Connect piping together usually.