Skipping around a bit, and quickly covering the three characters from the comics in the movie that are members of the Suicide Squad who haven't been covered in previous Suicide Squad articles here with more coverage of Harley Quinn and Killer Croc to come later!
Check with your local comic store for reprints of these and many other Harley Quinn stories.
King Shark....), but they both were monsters, who occasionally ate humans....and you can find more on Killer Croc on the just released Batman: Arkham Asylum: Killer Croc tradepaperback.
Suicide Squad, when the Squad (including Multiplex, Killer Frost, Deadshot, Rick Flag and Captain Boomerang) was sent to bring down Firestorm in Fury of Firestorm #64 (October, 1987) and Firestorm Annual #5 (1987), and, amazingly Slipknot survived this mission, only to get recruited again as the Manhunters attacked Earth in the Millennium mini-series of 1988, getting his arm blown off (thanks to encouragement by Captain Boomerang) in Suicide Squad #9 (January, 1988).
the Outsiders and the Suicide Squad, as revealed in Identity Crisis #4 of November, 2004). Slipknot later ran afoul of Ink (the newer version of Tattooed Man) during the Final Crisis Aftermath: Ink mini-series of 2009, leading to a final confrontation between the two in Titans #31 (March, 2011), with Ink the one coming out alive to greet his teammates of Deathstroke, Arsenal and Cheshire.
All of Slipknot's later appearances starting with Millennium have been collected (mostly as Millennium, Suicide Squad in the Nightshade Odyssey, and the Final Crisis and Titans in collections of their books), but his Fury of Firestorm and Blue Devil appearances still need to be roped in.....