I teach 8th grade English, and here is what I would recommend. I divided my selections into "Oldies but Goodies" sort of classics, but also included some recently released titles worth reading as well:
Oldies but Goodies:
Ender's Game by Orson Scott Card-- Dystopian with a science fiction twist, in this novel humanity faces destruction by alien bugs. The military experts decide they need a genius strategist to save the world and begin training exceptional children with video games.
Lord of the Flies by William Golding-- This novel takes dystopian to an all new level when boys stranded on a deserted island begin turning savage.
Fahrenheit 451 by Ray Bradbury-- Set in Bradbury's futuristic world of 1991 (hey, but he first wrote it in the 1950s), this novel has many startlingly close similarities to our modern society, except for the part about firemen who set fires instead of putting them out.
New and Exciting:
The Hunger Games series-- These books are super-popular right now for a reason, and their dystopian elements are cool enough to entertain readers but also challenge their perspective on entertainment and violence.
The Eleventh Plague by Jeff Hirsch-- In this novel, America has been decimated by a plague, and uses one small town's experience to define important themes like survival, loyalty, and family.
GONE by Michael Grant-- My students love this series, which begins like a modern day Lord of the Flies set in California. All of the adults mysteriously disappear, and the remaining kids must make sense of a world without supervision or rules.