Best "master" file
 

I am editing HD 24p in Sony Vegas having captured with a cineform encoder.I
will apply edits then render out and place this rendered file into Expression Media (using the very nice and free for now Expression encoder)
for various web projects. I don't expect anymore than web use but what would
you reccomend as the best container for the NLE rendered footage.
Would rather not save a uncompressed 1920X1080 AVI
but don't want to recompress the already compressed.
Looking for best guess only not the "official" word.