PSP/Official Extras

SensMe Channels
Go to http://www.playstation.com/psp-app/sensme/en/download_pc.html to install SensMe

X-radar Portable
A digital walking map for the whole of Japan. It uses, but does not need the GPS accessory.

Your PSP needs to be set to a Japanese locale to see the app.

Go to https://wowroms.com/en/isos/playstation-portable/x-radar-portable/34705.html to download (107MB)

Digital Comics (OBSOLETE)
Sony closed the service on October 30, 2012, and has long since removed the application.