I've been wanting to have the PSP able to use an external source of memory for a while. When researching the new updates for the PSP such as the custom firmware extender it has some key points to how it is possible to pull iso's, mp3s, pictures, movies etc from a hard drive. Though one drawback was the need to have a computer act as the USB Host as the PSP does not have a USB host built in.
* Stream ISOs via USB.
* Start and stop USB Mass Storage under the VSH (PSP Menu) while browsing
* Enable USB Mass Storage at startup.
Now the problems,
1. I don't want to use a pc/ or laptop as a mediator between me and my PSP
2. USB Host mode, to make a controller or find a solution that has one built in
3. If I get a portable hard drive that has a built in USB controller, what about powering it, I don't want to lose the portablility.
4. Cost, there are devices like the rhapsody that have been around for a while that contain 2 or more USB host controllers as well as a ton of bells and whistles, (which would be nice but defeats the purpose of using the PSP to do it)
1,2. Newegg.com had a sale on a portable USB HDD enclosure that you can put any notebook HDD in.
As for the power, that's simple enough any setup with a li-ion battery that has it's voltage regulated to 5v would provide enough power.
(This is the next step I'll be working on as my HDD enclosure is to be delivered today)
I'll provide the exact steps I do to get it working, and if I can I'll post pictures with captions per the steps.