Niagara 1814 is a scenario book for Blackpowder. As with any book of scenarios, however, they can be adapted to whatever rules set you play
Gnome Stew has an interesting form to help you plan gaming adventures. It gives the game master a place to record locales, story goals, adversaries and treasures. It is intended for role playing, but I think it also would be useful for those story-driven miniatures skirmish games.
Here’s a scan of a classic Viking raid scenario from a twenty year old Practical Wargamer issue.
From Wargames World, here’s a scenario for Killiecrankie. Occurring in 1689, its another of the seemingly endless string of conflicts between Scots and English government forces.
A Miniature History of the American Revolution has orders of battle for Guilford Court House, the famous battle in the Southern Campaign of the American Revolution.