I've noticed with some of my stories that even if i finish a section of story I always seem to think of something else for the scene a few more scenes in.
Does this happen to you? How often?
What'd really be spiffy is a writer's version of Subversion (archiving program for software developers). I'd love to be able to have branches and tags for a story. There has actually been a fair amount of discussion on the subject, but alas it appears to be much more difficult to track storytelling that it is to track code.
What's "something else", exactly?
I mean, are we just talking cosmetic changes or do you actually add substantial content to the story?
I use Scrivener's text snapshot function to version my stories and novels. You can look at and compare old versions with new and can revert back when necessary. You can name your snapshots and the snapshots are dated. The way I organize things is before I do a major draft pass I take a snapshot off all my scenes and name them something like Draft-03, so I know that all those scene versions belong together and I consider them collectively as a stable build.
Ideas of any kind ranging from a small sentence to whole section of story.