This very useful new book by Robert Reinhardt has just been published by Peachpit Press. This new book covers in-depth the preparation and delivery of video for the web via Flash CS4 Professional.
2 chapter excerpts have been posted to the web:
In particular, page 3 of the Compression and Encoding Primer covers the Sorenson Spark and On2 VP6 codecs primarily used with Flash.
Please take a look at these excerpts. They should be very helpful to all of you getting up to speed with Flash video. And let me know in the comments what you think of them.