As for things that do exist today, The Expendables 2 is a thing you can pay money to download, and is joined by PS2 Classic War of the Monsters and the aforementioned Transformers: War for Cybertron demo – you don't have to pay money for that last thing. Pre-orders for next week's release, Sound Shapes, are also open – it's 20% off for PS Plus members and all pre-orderers will receive a free PS3 theme. We haven't seen the theme, but it probably has some shapes in it, probably not much in the way of sound.
Update: According to a comment on the PlayStation Blog from Morgan Haro, community manager for digital platforms at PlayStation, the reason GTA 3 isn't available for download this week is due to a licensing issue involving the soundtrack. "There were some last minute issues with getting clearance for a certain audio track in the game; but the teams at Rockstar are on it to review how to best get this title on PSN."
Sony PlayStation 3 (late 2012)
Sony PlayStation Portable PSP-2000