I'm planning a tour of the Anglo-Boer battlegrounds (e.g. Magersfontein) and significant sites (e.g. where Winston Churchill was captured) in South Africa. I'm getting all the locations and backstories from Wikipedia, websites, and books.
That got me thinking that it would be nice if there was a website where users can post self-guided themed tours, e.g. "Locations of the Second Boer War", or "The path of the Klondike Gold Rush", or "The footsteps of Jack The Ripper" (which actually exists at http://www.freetoursbyfoot.com/london-tours/self-guided-walking-tour-of-jack-the-ripper-sites/), etc.
Although some specific themed self-guided tours exist (like the link above), it would be nice if there was a single crowdsourced site (possibly a wiki). http://www.freetoursbyfoot.com/ is quite a nice format with locations and explanations of the significance of the locations, but being a private site it has limited tours (e.g. no SA tours).