On one of the other forums I kinda frequent (and other users from here do too), they have "off-topic" buttons that seem to work quite well.
Basically all of the off-topic material (which inevitably always appears on AN, despite max moderation and clear-cut forum rules) is only view-able to those who click the button (which opens the off-topic content).
Example:
http://www.medstudentsonline.com.au/f48/should-you-prepare-umat-9664/index4.html#post238777Okay, that example isn't great because that post has 0% on-topic material, but at least users don't have to go through reading a massive post (I could link a few recent ones here if needs be - but I'd rather not bring them up again) to realise that it's of topic. They can see the button on the post and skip it if they want. It looks cleaner (organisation and length of page) and it's easier to tell what is and isn't on topic.
One argument that came up on IRC when I proposed this idea was that it would encourage more off-topic posts. Rather, I think it would help mods find WHO are the off-topic posters are more easily (to issue warnings/whatever, or to just leave things as they are). But as mentioned above, as off-topic discussion is always going to happen (and tbh, some of it is pretty funny/interesting), having such an option just makes everything look better

Another point is that "who will mark their own comments as off-topic", well with this button in place, obviously off-topic convo NOT marked as so by the user will be far more harshly dealt by than such comments marked as off-topic (ideally, comments marked as offtopic by the user would have NO penalties, but this is just my opinion haha).
Dunno, just something I thought was cool from another forum that might work here

Thoughts?
N.B. it is the users who insert info into the off-topic boxes using something like [offtopic]...[/offtopic] or even something shorter like [off]...[/off] when they make their post (it would be one of those posting options like the latex, bold, underline, etc options when posting), not the mods

Should have made that clearer
EDIT: ADDED BENEFIT AS DESCRIBED BY LASEREDD:
oh, I just remembered, an off-topic button could also double up to be a spoiler tag - which would be handy for those general discussion threads about movies, anime etc. and also could come in use when you have people writing using really small to hide answers etc.
ie. use for spoilers and quizzes too!