I find spinoff threads to be very useful for keeping things on topic.
It might be nice if there were an option when replying to a thread to check a box or something and create a spinoff automatically. This would make a new thread with the OP as your quoted post, and leave a generated link to that new thread in the old thread (the link would be the name of the spinoff thread).
I've had to do this manually from time to time, and it usually turns out well.
I know people might go crazy with it. I just think I would find it useful personally.
Just a notion.
EDIT: You would probably want a drop-down list to select which forum it would go too, since often times spinoff threads can deal with different topics, that's what made them OT to begin with.
*nudge* because this was posted on a holiday.