It's not quite Gran Turismo 4 Prologue, but for most of us in the States, it will have to do...
Recently, the word went out that a free demo was available for Gran Turismo 4. You, I, or anyone else can get it. That's the good news. The bad news is that it requires a lot of filling out alot of forms and requesting other materials from Toyota's website. Apparently, logging onto the website and requesting various information on the Prius hybrid and other things will net you one Gran Turismo 4 demo disc, along with some brochures and flyers about various Toyota products. The disc is apparently the same that was offered at Japanese Toyota dealers and the New York Auto Show last year. It reportedly has two cars (Prius and the Toyota MTRC Concept) and two tracks (the Fuji Speedway and Grand Canyon).
News source: GameDAILY