See Doctor Who Series Four Monsters
The BBC Put up three very short teasers. They give a burlesque style teasing view of what three of the monsters will look like for series four. The Ood, Sontaran and Dalek. BBC did a great job with these because they show enough that the imagination could fill in the rest with out showing everything. Even with the Dalek they did a great job. We all know what the new Dalek looks like seeing it in series one but they show someone reflected in the end of it's blaster. I wished they were longer.
Here is a link to BBC Triple teaser trailers to watch them for yourself.