PlayStation Life, the PS3's global news service, is a neat screensaver, but its gaming applications have been somewhat limited to date. Something that may change with the addition of game trailers to the service.
The new "PlayStation Network Game Trailers Channel" (catchy!) has recently gone live, and allows you to both stream a whole bunch of clips for PS3 games, and if applicable, buy them from the PlayStation Store as well.
At the moment it's only available for those with a US account. Like, people with a real US account; I couldn't access the channel using my US account in Australia.