Square-Enix has let slip what they'll be showing off at their booth during E3. Per usual, this is subject to change in consideration of any bombs that may be dropped during the actual event. Bolded items are for Playstation products.
Final Fantasy XII – Playable
Valkyrie Profiles 2 – Playable
Final Fantasy VII: Dirge of Cerberus – Playable
Dawn of Mana (Seiken Densetsu 4) – Video
Final Fantasy XI: Treasures of Aht Urhgan – Playable
Final Fantasy III – Playable
Valkyrie Profiles: Lenneth – Playable
Seiken Densetsu DS: Children of Mana – Playable
Final Fantasy IV Advance – Video
Final Fantasy VI – Video
Rocket Slime – Playable
Conspicuously absent from the list is Crisis Core-FF7 for the PSP, although a Famitsu article states that it is slated to appear at E3.