Here's a list of 19 of 27 confirmed playable PS3 titles. The publisher for each game is listed in parentheses.
Devil May Cry 4 (Capcom)
Fatal Inertia (Koei)
Blade Storm (Koei)
Mahjong Taikai IV (Koei)
Coded Arms Assault (Konami Digital Entertainment)
Formula One World Championship (SCEJ)
Heavenly Sword (SCEJ)
Resistance Fall of Man (SCEJ)
The Eye of Judgment (SCEJ)
Gran Turismo Series (SCEJ)
Minna no Golf 5 (aka Hot Shots Golf, SCEJ)
Ridge Racer (Bandai Namco Games)
Gundam Target in Sight (Bandai Namco Games)
Armored Core 4 (From Software)
All but the first game were previously announced. Given its publisher (and title), the first game is likely a train simulation game of some form.
The remaining 8 titles are currently a mystery, so we encourage wild speculation.
Sony will also have a theater in its booth which will show video footage of a total of 35 titles. We presume there will be some overlap with the playable titles and the video-only titles, but Sony wasn't clear about the matter.