At this year's E3, Irrational Games released a new teaser trailer for BioShock Infinite which you can view here or below. In addition, there's also a ViDoc entitled "About Skylanes" which explains this interesting mode of transportation around Columbia, and it can be viewed here or below.
Three new screenshots for the game are also available for viewing on the official site here.
Overall, very ambitious looking, as is any game that Ken Levine puts his hands on. Quite exciting!