Diablo 3 is due out this year, possibly even next month, and I for one am looking forward to it! I play a lot of World of Warcraft, mainly working the Auction House and making gold, and Diablo 3 is going to have a "real money" Auction House. It probably wont make me rich, but it's always nice if your hobby generates some income ;)

Back on topic, there's a great Gamasutra article titled "Postmortem: Blizzard's Diablo II" which gives you an inside look in to the development that went in to Diablo 2 and lessons learned from Diablo 1, etc - some interesting stuff.

Next up are three great YouTube videos by "Force Strategy Gaming", covering the Diablo Lore leading up to Diablo 3, a great way to catchup before the releases:

Part 1 - Pre-Diablo:

Part 2 - Diablo 1:

Part 3 - Diablo 2: