OnLive Service
Streaming PC games online. Subscription based service where you play pretty much ANY pc game remotely on their servers, no need to download it to your computer or have any dedicated gaming hardware (fast CPU, GPU, directx 10, etc). Works on Windows, OSX, and on a regular TV with their little set-top box.
Seems too good to be true to me, but we'll see... They're taking beta applications as we speak.
http://www.onlive.com/
Gears of War 2: Dark Corners
Campaign DLC expansion pack for Gears 2, no full announcement on it yet, but it was leaked on the japanese marketplace site.
http://n4g.com/events_gdc2009/News-299573.aspx
Ninja Gaiden Sigma 2
360 "exclusive" goes PS3, now with Ayane playable and online co-op.
CryEngine 3.0 Tech Revealed
Just when we get to the point where a regular gamer's PC can play Crysis... they roll this shit out. (Although with OnLive this supposedly wont' be an issue

Looks great, as expected. But I have to question... have they even recouped the costs of developing CryEngine2 yet? There's only 3 games that use it, 2 of which are Crysis titles, and one is just an indie game...
Noby Noby Boy Multiplayer Mode
Let the sausage-fest commence!
More Punch Out Footage
Wii Firmware 4.0
Available now, supports SDHC with up to 32 gig SD cards. Direct download from the Wii Shop to your card AND most importantly the ability to launch WiiWare and Virtual Console titles directly from the memory card. They also added "Arcade" games to VC, with a bunch of Namco arcade classics (Mappy, GAPLUS, Solvalou, etc) to start it off. Hopefully they get some CPS2 classics on there, I'd totally be down for that.
Max Payne 3 announced for 2009
Coming to all platforms that matter (PC, 360, PS3).
http://ps3.ign.com/articles/965/965132p1.html

Final Fantasy Coming to Wii VC
Square will be releasing FF1 and FF4 on VC, as well as original titles "My Life as a Dark Lord" and "Final Fantasy 4: The After Years" onto WiiWare.
New Zelda Game "Spirit Tracks" on DS
Links drives a train.

http://www.joystiq.com/tag/@nintendo-gdc-megatons