Paul Allen's Twitter seems to be a good source of up-to-the-minute news on the dive: https://twitter.com/#!/PaulGAllen

He says he's on "Octopus," which I assume is one of the support vessels. Aparently Cameron's sub has just touched down on the seabed, Allen's latest tweet:

#deepseachallenge hit bottom at 0752 local time "All systems ok"

and a few minutes before that:

"Now on the bottom 35755 ft!! Plan is for #Deepseachallenge to spend 4-6 hours on the seabed- take samples....Huge Congrats what a relief!!!"

Very exciting!