Official Website: http://www.worldofwarcraft.com/wrath/
(info on 2 zones, lore info)
Official FAQ: http://www.worldofwarcraft.com/wrath/faq.xml
(Read this)
Official trailer: http://www.worldofwarcraft.com/wrath/movies.xml
(Not a cinematic; spliced from ingame footage; quick glimpse of deathknight, arthas)
Blog of the Demo Panel: http://www.wowinsider.com/2007/08/03/liveblogging-the-blizzcon-expansion-demo-panel/#comments
(contains deathknight info, info on initial zones)
Blog of the Class Panel:
http://www.wowinsider.com/2007/08/03/l/
(contains information on how classes have changed from release to now, post TBC; each class' weaknesses, and how/if they'll fix them. Also contains Q&A section; most questions were about hybrid classes (paladins/shamans/priests)
Blog of the Raid/Dungeon Panel:
http://www.wowinsider.com/2007/08/03/liveblogging-blizzcons-dungeons-and-raids-panel/
(nformation on how dungeons are developed, how they balance them, and what does/doesn't work)
1up webpage:
http://www.1up.com/do/newsStory?cId=3161725
(information on deathknights primarily, also some information on new profession- "inscription")

WoWWIKI:
http://www.wowwiki.com/World_of_Warcraft:_Wrath_of_the_Lich_King
(dynamic wiki page)

Live stream of blizzcon: http://www.giga.de/2/live/free/
(cuts to other things occasionally, may not be focused on anything related to WoW)
The stream is currently focusing on... Nothing

So what is inscription?

Inscription is a new tradeskill; summarized as "Enchanting for your spells and abilties". How the profession works has not yet been explained, but apparently this adds new effects and/or improves your abilities.

Mentioned were increased haste rating, increased damage/healing, increased crit rating, increased range, and adding a knockback effect to a spell.

So what are Deathknights?

Deathknights are the first hero class, to be introduced with the expansion.

Creating a deathknight works as thus: Once you hit 80, you are given the option to do a new quest chain, comparable in difficulty to the "old warlock epic mount quest". Once you complete this you are given the option to create a deathknight character. Your old character is not "replaced" by the deathknight; and this is not paladin-specific; anyone can do this. Also confirmed is that any race can be a deathknight.

Deathknights start high-leveled already- 55ish at the minimum; 80 as the maximum (unconfirmed exactly what level). There are no exceptions; there will be no level 1 deathknights.

Deathknights are a tanking/DPS hybrid; sort of an "antipaladin". Also confirmed is that deathknights do not use shields; they tank with a 2h/by DWing.

The ability to summon undead minions is confirmed, though Death Knights are not a pet class and this is more of a treant/shadowfiend type of ability.

Deathknights do not use mana, rage, or energy. Instead they have a "rune system". When you are out of combat, you can switch your active runes around a few types; you have 6 rune slots. Abilities will put certain rune types on cooldowns or may even use multiple runes. Thus, what runes you choose affect how your deathknight plays in combat.