The Argonnessen Prophecies
Tools for Eberron Newbies
Okay, so, the simplest way for you to learn everything you need to play is to get the Eberron Player’s Guide for 4e… but maybe you’re cheap and you don’t want to buy the book. Believe me, I understand.
The Eberron Wiki is a good source of getting all of the “fluff”, like learning what Halflings are like in Eberron (either city dwellers or barbarian dinousaur riders. Not kidding), what the major power factions are, overview of the history of the war, etc.
Of particular interest: if you are planning on taking a Dragonmark should read up on The Dragonmarked Houses to figure out which house they would like to be a part of, if they are taking a “legitimate” mark.
You can also find a timeline that might lead you to character ideas.
Honestly, this is the best “free” resource to looking stuff up, but you should also know that it might reveal info that your PC should not have. As players in my game, I trust you all to be able to separate “player knowledge” from “character knowledge”.