How To: 20GB External Storage for PSP
Check out this interesting how-to on using an external hard drive enclosure with built-in WiFi connection to add more storage space to your PSP (well, sorta).
Note that ADS sells an
enclosure that I cover in my book,
Hacking the PSP, that enables you to access your files via your PSP's web browser. It's only $99 and may be easier if you just want to access your files, such as your music, video, and more from your PSP without any firmware modifications.
-Auri