Good news for expat gamers - Playstation 3 titles are entirely region free. The console’s menu screens can also be set to English, unlike the Nintendo Wii.
As for the games you can buy in Japan:
Japanese version has English option:
Def Jam Icon
Devil May Cry 4
Fight Night Round 3
Ninja Gaiden Sigma
Mobile Suit Gundam: Target in Sight
Power Smash 3
Ratchet and Clank - Tools of Destruction
Resistance Fall of Man
Ridge Racer 7 (also supports other languages)
Sonic the Hedgehog
Uncharted: Drake’s Fortune (Japanese version is partially censored)
Virtua Fighter 5
Warhawk
Winning Eleven 2008
Japanese version lacks full English:
Assasin’s Creed
Call of Duty 4
Enchant Arm
Everybody’s Golf 5
Formula 1 Championship Edition
Genji: Days of the Blade
Guitar Hero 3 (The training is in Japanese, but most of the game is English)
Gundam: Musou
Heavenly Sword
Mahjong Kakutou Club / Mahjong Fight Club
Mahjong Taikai IV
Miyasato Miyoshi Kyoudai Naizou: Sega Golf Club
Motorstorm
NBA Live 2008
Need for Speed Carbon
Record of Agarest War
Rise from Lair (Lair)
Shin Sengoku Musou 5
The Elder Scrolls IV: Oblivion
The Godfather (English audio)
Motorstorm: The Japanese version doesn`t support online battles.
PSP
The PSP is also region free for games.
Games where the Japanese version has an English option:
Final Fantasy Anniversary Edition
Final Fantasy II Anniversary Edition