IGN have have compiled together a well written story about the History of Halo, everything from the early beginnings of Halo on the Mac, to the talks and hype of Halo 3.

There's even some very interesting facts in there too, like we were supposed to "Finish the Fight" in Halo 2, and Take-Two (makers of early GTA games) partnered with Bungie to make Halo, but soon split up after Microsoft bought Bungie - that means if Microsoft never made a deal Halo would have come over to Playstation just as GTA had.

Anyway, it's a great read and all the comments seem to agree too.
A must-read to anyone who wants to catch up on Halo before the big release, learn more about the makings of each game, or is just interested in the storyline or anything of the sort.