Tomorrow is Bungie Day for the Halo 3 developer, as they've celebrated every July 7 in recent memory. Since it will be 2007 (i.e. 7/7/07, or triple 7s), there is some "extra special content" coming to Xbox Live Marketplace, according to the developer's website, in addition to new content on Bungie.net itself.
As to what the goodies will be, exactly, Bungie isn't saying -- "don't get too excited, it's not Halo 3," said the newsbrief. We're predicting gamertag pictures, themes, and the like, of either Halo, Marathon or their long-running joke Pimps at Sea.
Regardless of what the content is, there's only a small window of opportunity, as the mysterious content will only be available from 5:00 am ET until 3:00 am on Sunday.