Only a rumour for now, but EA's press release regarding their E3 lineup shows Left 4 Dead as X360 and PS3:
- Dead Space (Xbox 360, PS3)
- FaceBreaker (Wii, Xbox 360, PS3)
- HASBRO FAMILY GAME NIGHT (Wii, PS2)
- LITTLEST PET SHOP (Wii, DS, PC)
- Madden NFL 09 (every system under the sun)
- Mercenaries 2: World in Flames (Xbox 360, PS3)
- Mirror's Edge (Xbox 360, PS3)
- The Sims 2 Apartment Pets (Nintendo DS)
- Zubo (Nintendo DS)
- MySims (PC)
- MySims Kingdom (Wii, Nintendo DS)
- Spore (PC)
- Tiger Woods PGA TOUR 09 (Xbox 360, PS3, Wii, PSP)
- Warhammer® Online: Age of Reckoning (PC)
- Command & Conquer Red Alert 3 (PC)
- Crysis Warhead (PC)
- Harry Potter and the Half-Blood Prince (Wii, PS3, 360, PS2, PSP, DS, PC, Mac)
- The Lord of the Rings: Conquest (multi)
- SimCity Creator for (Wii)
- NBA LIVE 09 (Xbox 360, PS3)
- NCAA FOOTBALL 09 (multi)
- Skate It (Wii, DS)
- Rock Band 2 (Xbox 360, PS3, Wii)
- Left 4 Dead (Xbox 360, PS3)
http://www.gamepro.com/news.cfm?article_id=199448
Half Life 2: Episode 3 is also rumoured to be ported for the PS3, so good news for the triple-only owners.