Updated (I've removed some of the long-dormant projects):
Adam Strange
Warner Bros.
Comment: Warners is taking pitches for an Adam Strange film. Leonardo DiCaprio's production company Appian Way may be involved in developing the film.
Aquaman
Warner Bros.
Comment: Leonardo DiCaprio's production company Appian Way is developing the film.
Batman Begins III
Warner Bros.
Directed by Christopher Nolan (pending confirmation).
Produced by Charles Roven, Emma Thomas, and Christopher Nolan (pending confirmation).
Comment: This looks likely to be a summer 2012 release.
Billy Batson and the Legend of Shazam
Warner Bros.
Directed by Peter Segal.
Produced by Michael Uslan, Peter Ewing, and Peter Segal.
Written by John August.
Comment: John August has said project isn't happening, at least not this version of it. Michael Uslan claimed the contrary, saying there's life in it yet. The Hollywood Reporter still lists it as one of the DC films currently in development.
Bizzaro Superman
Warner Bros.
Written by David Howard and Robert Gordon.
Constantine 2
Warner Bros.
Produced by Akiva Goldsman and Erwin Stoff.
Comment: The film is in development according to The Hollywood Reporter.
Deadman
Warner Bros.
Directed by Guillermo del Toro (possibly).
Produced by Guillermo del Toro, Don Murphy, and Susan Montford.
Written by Gary Dauberman.
Comment: To say that del Toro has a lot on his plate is an understatement, so whether this project will ever get made is unclear.
Death: The High Cost of Living
Warner Bros.
Written and directed by Neil Gaiman.
Produced by Don Murphy and Susan Montford (with Guillermo del Toro as Executive Producer).
Comment: This has been in development for years and every time Gaiman says it seems to be imminent nothing comes of it.
The Doom Patrol
Warner Bros
Produced by Akiva Goldsman and Kerry Foster.
Written by Adam Turner.
Comment: Akiva Goldsman has said that the material is so esoteric that he doesn't think the film will come to fruition.
Ex Machina
New Line Cinema.
Produced by Chris Bender and J.C. Spink
Written by Brian K. Vaughan and Glen Brunswick.
Comment: This was set up at New Line about four years ago. Its status is unknown now that New Line has been folded into WB.
The Flash
Warner Bros.
Produced by Charles Roven, Alex Gartner, and Geoff Johns.
Written by Dan Mazeau
Comment: Mazeau has been working from a treatment written by Geoff Johns. The film currently doesn't have a director attached. It's unclear whether Charles Roven is still involved as producer.
Green Arrow: Escape from Super Max
Warner Bros.
Written by David Goyer and Justin Marks.
Comment: According to The Hollywood Reporter, Warners also has an alternate Green Arrow script in development, one that's a more straightforward origin story.
Green Lantern
Warner Bros.
Directed by Martin Campbell.
Produced by Donald DeLine and Greg Berlanti.
Written by Greg Berlanti, Marc Guggenheim, and Michael Green.
Starring Ryan Reynolds.
Comment: Scheduled to start production in January for release on June 17th, 2011.
The Human Target (TV)
The Fox series, starring Mark Valley, will premiere on January 17th, 2010.
Jonah Hex
Warner Bros.
Directed by Jimmy Hayward.
Produced by Andrew Lazar and Akiva Goldsman.
Written by Mark Neveldine and Brian Taylor.
Starring James Brolin, Megan Fox, and John Malkovich.
Comment: Scheduled for release on June 18th, 2010.
Lobo
Warner Bros.
Produced by Joel Silver.
The Losers
Warner Bros.
Directed by Sylvain White.
Produced by Joel Silver, Akiva Goldsman, and Kerry Foster.
Written by James Vanderbilt and Peter Berg.
Starring Jeffrey Dean Morgan, Zoe Saldana, Chris Evans, Jason Patric, and Columbus Short.
Comment: Scheduled for release on 16th April, 2010.
Metal Men
Warner Bros.
Produced by Lauren Schuler Donner.
Written by Eric Champnella.
Plastic Man
Warner Bros.
Written and directed by Larry and Andy Wachowski.
Comment: The Wachowskis first wrote a script for this over a decade ago; some of the recent reports that this may be their next film have either been debunked or seem dubious, so it's unclear whether the Wachowskis are still actively developing the project.
Preacher
Columbia Pictures.
Directed by Sam Mendes.
Produced by Neal Moritz.
Red
Summit Entertainment.
Produced by Lorenzo di Bonaventura and Mark Vahradian.
Written by Erich and Jon Hoeber.
Starring Bruce Willis and Morgan Freeman.
Ronin
Warner Bros.
Directed by Sylvain White.
Produced by Gianni Nunnari.
Written by Peter Aperlo and Sylvain White.
Sgt Rock
Warner Bros.
Directed by Guy Ritchie.
Produced by Joel Silver.
Written by John Cox.
Comment: Ritchie has said he's still very keen to make the film even though Sherlock Holmes has waylaid him from it for the time being.
Suicide Squad
Warner Bros.
Produced by Dan Lin and Stephen Gilchrist.
Written by Justin Marks.
Superman
Comment: Brandon Routh's contract to play Superman has expired. News reports indicate that WB may need to start production of a new Superman film by 2011 to avoid legal setbacks.
Teen Titans
Warner Bros.
Produced by Akiva Goldsman and Kerry Foster.
Written by Mark Verheiden.
Comment: The extent, if any, of Akiva Goldman's continued involvement isn't clear.
Wonder Woman
Warner Bros.
Produced by Joel Silver.
Comment: Silver bought a screenplay by Matthew Jennison and Brent Strickland two years ago, but there's been no news since.
Y: The Last Man
Warner Bros/New Line Cinema.
Directed by D.J. Caruso.
Produced by David Goyer, Chris Bender, J.C. Spink and Mason Novick.
Written by Carl Ellsworth.
Comment: D.J. Caruso has said he's still intent on making the film, but he's signed on to make another film first.