I didn’t know there was an old one, but Major Nelson just posted there is now a fancy new Xbox Engineering Blog:
Welcome to the new home for the Xbox Engineering Blog. This is a place where the Xbox development team will communicate directly with you. We’ll share information straight from the people that develop, test, manage, release, and maintain the Xbox 360 and its services. I am a part of this team as a software development engineer in test, working on community features such as friends and parties, and I am happy to introduce you to this new space. As with the previous blog, my co-workers and I will continue to share tips and tricks about the Xbox, and give you a closer look at the people and science behind Xbox 360. We’ll start off by giving you a behind the scenes look at some of the technology that went into recent releases of the Xbox 360 system software. You can expect to hear from us about a couple times a month.
http://www.xbox.com/en-US/live/engineeringblog/default.htm
Worth keeping an eye on.
Ive set up a new twitter called XboxLiveDLC, which grabs the marketplace RSS feed from Major Nelson’s blog. It will tweet the downloadable content, price and any other info that fits in 140 character limit along with a link to the relevant article on Major Nelson, as new content appears.

http://www.twitter.com/XboxLiveDLC
Its automatic, and appears to be working so far, currently its grabbed the info on the Fable 2 Knothole Island DLC which released yesterday.
Just noticed on Major Nelsons Marketplace RSS feed that a Dead Space demo is now available, and thought it would be a good chance to try out the queuing feature that was included with last weeks NXE dashboard update.

So if you haven’t got access to your 360 whilst your reading this, hit this link for the marketplace at Xbox.com, sign-in with your account and click the download link to queue it up. The demo will begin downloding automatically the next time you turn your 360 on. Nice.
EDIT: The link above is probably for the EU Marketplace, the US maybe a different link. Either way head over to Xbox.com and hover on the Xbox LIVE tab, and then select Xbox LIVE Marketplace for your region.