Rock, Paper, Shotgun has put together a nice little list of where each member of the ESA stand on SOPA. While many of the member companies have not responded, the list shows that - when pressed - many don't support it.
According to the list, 345 Games (who are owned by Viacom, who do support it), 505 Games, Deep Silver, Disney Interactive Studios (parent company supports it), Her Interactive, Ignition Entertainment, Konami Digital Entertainment, LEVEL-5, Namco Bandai Games America, Natsume, Nintendo of America, NVIDIA, O-Games, Perfect World Entertainment, SEGA of America, Slang, Square Enix, Tecmo Koei America Corporation, Take-Two Interactive Software, THQ, Ubisoft, Warner Bros. Interactive Entertainment, and XSEED Games have all been contacted. All of these companies don't have a specific position on SOPA.
Companies that have come out firmly against include Epic Games, 38 Studios, Nival, and Trion Worlds. Only Capcom has said that they support the efforts of the ESA. Other companies are inexplicably tied to support of the bill because their parent companies do.
Nexon and EA have said that they do not have a public position on SOPA.
Some of those companies listed above do have parent companies that support SOPA directly. You can check out the full list here. We suspect that it will change once these companies respond to press inquiries about their positions.