In general, the rule of thumb is to place it wherever feels best to you, and if the mods think theres a better place, theyll move it on their own.
HAVING SAID THAT
Things like campaign journals are a bit tricky on these boards, because they're discussion forums, not a wordpad for you to keep your personal notes. Campaign Journals and Lets Plays and the like are not exempt from the double posting rule. If you dont think your journal will foster discussion pretty frequently, it may be better to not post it at all, and find some other place to host it. If you still want people here to be able to see it, and neither it nor the site that is hosting it violate the board rules, you would probably be best served by including a link in your signature.