Step 1: The obvious
Video- Having videos on your PSP really makes a difference on road trips. There are free programs on the Internet for converting videos into PSP forms, for example Orbit .
Music- Unless you have a Ipod, the PSP is also good for just listening to music.
Pictures- Showing pictures on your PSP to your friends, and you can also set it as your background.
Internet- The PSP internet is fun when you don't want to carry your laptop around. It can't support large sums flash, so no videos, no games, no porn (unless its pictures:)