What is in that damn box!?
Half Life EP3? A new phone? A trailer for a movie? Who knows! Valve claim it's not their doing but it wouldn't make sense if they admitted to their viral campaign that is getting everything pumped up about it.
Personally I think it's a trailer for a pre-HL2 type mod or film. Here's a link to a YT movie: http://www.youtube.com/watch?v=IU_reTt7Hj4 and you can google all about the box thing and the hidden content that people are trying to figure out.
Ah, I love these sort of mystery viral campaigns and looking in threads to see what people have figured out.
*edit* So it turns out my theory was stupid and so forth. Turns out the 00000's spell out a number which means in 4 days we'll find out what is in the box. Stay tuned.