This is a scene from my latest solo animation project, titled "A Viking's Quest."
All effects are done in Adobe Flash. The fog effects are the easiest, as they comprise of a Movie Clip symbol of a shape tween and given alpha transparency and a thick blur. Layer a few of these on top of each other, and you have a blur effect similar to the one seen here.
Of course, using Movie Clip symbols has a long history of being difficult to convert to video. However, since Flash CS3 was released Quick Time export has been capable of rendering Movie Clip symbols as they would play in a normal Flash file. Unfortunately, the way it works causes complex scenes to render poorly, resulting in choppy scenes as the program drops frames to keep up with the recording process.
My current plan to work around this is to export a version through this method as is, so that I have an accurate audio track. The next step will be to render the movie at around 4 frames per second so that I have a video containing all frames in their proper position. Then it's just a matter of bringing them both into a video editing program and finishing things up there.