Homer invoking the muse
Illustration by John Flaxman, engraving by William Blake
Picture sourceEnter The Iliad on a search engine and you will get close to one million matches. I only went through the first few pages of results and found the following links helpful:

Various versions of the text at Project Gutenberg
and at The Online Books Page
A list of English translations of Homer

The translation by Alexander Pope
and the illustrations by John Flaxman in Pope’s version

Translation by Ian Johnston
Translation by Samuel Butler at GreekMythology.com (which has links to other works, myths, characters and online works

A wonderful series of Essays on Homer’s Iliad at Ian Johnston’s site, covering many aspects of the work

The Wikipedia article on The Iliad

An introduction to The Iliad, complete with maps, outline, links, and other information (developed by Walter Englert for Reed College)

A guide to reading The Iliad, along with along with questions to keep in mind as you read plus a host of helpful links at the Classics Department of Grand Valley State University

Some approaches on teaching The Iliad from the Yale-New Haven Teachers Institute

Robert Fagles had an interview with The Paris Review.

Update (6 Dec 2012): The Iliad: Myth-Making Inside and Out by G.I.C. Robertson, on how the author re-shaped traditional stories for inclusion.