The list of free books would include:
- DM's Screen
- Magic Item Compendium I
- Adventure H3: Pyramid of Shadows
- Adventure P1: King of the Trollhaunt Warrens
- Martial Power: D&D Rules Expansion
A quote from Mike Mearles about running D&D without classes, something possible because of how the classes and powers are balanced:
Since many of the elements of character progression are unified, you could run classless D&D by allowing players to select maneuvers and spells from any class they want, mingling the two together, or start everyone with access to all heroic abilities and grant access to divine and arcane via feats.