If you haven't heard yet, there is a new title comming out for PSP.  ATV Offroad Fury Pro is going to boost the PSP console to a whole new level I suspect.  It can be traded with items on the new ATV ORF 4 on the PS2.  A ton of stuff can be traded between ATV Offroad Fury Pro on the PSP and ATV Offroad Fury 4 on the PlayStation 2. The Legend tracks, for example, can be opened on the PS2 by connecting the games together, as are the mini-games. Created tracks can also be swapped between the systems as both games will utilize the same construction parts.  This game takes track from the first three games and they are included in this one (Greatest hits) is the name. 
ATV Offroad Fury Pro is currently scheduled for release sometime in October, shortly after ATV Offroad Fury 4 on the PlayStation 2.

The PSP title separates itself from the fourth game on the PS2 by including unique race modes, vehicle classes, Legend tracks and much more.