We didn't really know what it was when it flashed up during the Sony conference, but upon getting home and sitting in front of our computer for ages (we're so hip), we learned that "Planet PSP" is a working title for a PSP-format "Lonely Planet" guide.
Lonely Planet, as you probably know, is a company that makes travel guides for all you losers who go outside sometimes. The initial Planet PSP release, due out this autumn, covers Amsterdam, Barcelona, London, Paris, Prague and Rome - and Sony plans to keep it all current with downloadable updates.
Aimed at "young city breakers and frequent travellers", Planet PSP will tell you about the best restaurants and clubs among other things, with maps, videos, "audio walks" (i.e. listen while you walk), lots of photographs, and itineraries - your own, and pre-planned ones for the lazy traveller.