Arms and Equipment (3.0) has a list of stone-age weapons and armor, as well as penalties for fighting with stone-tools.
Frostburn has alot of useful into: neanderthals, primitive weapons, etc.
As for classes: Fighter, Barbarian, Druid, Scout (CV), Savage Bard (UA), Sorcerer, Spirit Shaman (CD), Warlock (CA), Ranger, and Dragon Shaman (PH2) all fit thematically. Some tweaks and there you go.
Make all the classes illiterate, of course.
UA also has arctic and jungle racial variants, depending on if you want a lost-world or ice-age setting.
If you want metal weapons: consider a "fallen" world that has resorted to barbarism rather than a emerging world.