The first two dozen tweets from Trevor_WotC, in chronological order (earliest to later):
24. Mike Mearls and Rich Baker. Kirin Chase as well - Brand Manager for D&D. Bart Carol will be posting up the podcast later. 
23. Mike is talking about Underdark and Dragonborn book, touching on D&D Insider articles as well - nothing new yet. 
22. Rich: Goal for D&D Insider is that every character can find something useful every month. 
21. Rich: Martial power 2 in February - New Fighter build, 2 new ranger builds, new rogue build, and 2 new warlord builds 
20. Rich: New weapon style feat system which we think is going to be a lot of fun 
19. Rich: Of course new paragon paths and epic destinies. A lot of fun, had a lot of fun working on it. 
18. Everybody is clapping for Rob Schwalb, introduced by Rich - did some work on MP 2 
17. Rich: Martial practices is a new mechanic for doing heroic things, also in MP 2 
16. Rich: New 3 Dragon Ante. Expansion to the original and stand alone game 
15. Mike Mearls: PH3 and psionics! 
14. Mearls: New psionic power source classes: Monk - uses the power source but does not use power points 
13. Battlemind - Psion - , Monk - Ardent 
12. Mearls: We have tried in this book to provide a lot of options to those who don't plan on running psionic characters 
11. Mearls: Hybrid character class system is one of these, more skill powers, a few non psionic classes 
10. Mearls - Hammerfast coming in March. Return to the Nentir veil, more details on the town of Hammerfast. Poster map of the town 
9. Mearls - I wanted to put twists, hooks with every character/npc interaction. Something unique to spark an interesting interaction 
8. Mearls - New set of Dungeon Tiles "Harrowing Halls" 3D Tiles included 
7. Mearlsl - Plane Above in April/May as well as Player's strategy guide 
6. Player's Strat guide is a fun engaging read, several different authors - celebrities in the D&D field - tips, tricks, and stories 
5. In May, Dungeon Magazine Annual - best articles of past Dungeon releases. 
4. Also The Slaying Stone, soft cover adventure for low level characters. Double sided poster map. 
3. Monster Manual 3 hits in June! (People oooohing at the image of the orcus "miniature" ) 
2. We got feedback that the MMs didn't have enough flavor, so we're changing the format. We'll be putting a bit more story/hooks/descriptions.. 
1. for monsters to give it more of a story.