Just a quick couple of suggestions for people looking for something a little more original than The Loch Ness Monster, Atlantis, or Alien Abductions to work into their creative endeavors. (Because they occurred to me while I was wandering Wikipedia and this is my blog)
First, think long and hard before writing stories about lost technology or an Advanced Ancient Acropolis. It’s far too easy to get caught up in the excitement of writing them and misjudge your ability to do them well. (And, more subjectively, I’m getting tired of reading about them too)
Second, please please please don’t write a You Go Too Far! story. Science Is Bad stories are far too common and, given how you probably wouldn’t have time to write without its fruits, it’s, at best, frustratingly hypocritical and ungrateful to add to the pile of fiction implying that all progress is bad. I see your Frankenstein and raise you Plato’s Cave.
Finally, if you’re going to build your story on unsolved mysteries, vive le difference. Open up Wikipedia’s Open problems category and drill down to something like Undeciphered writing systems or Uncracked codes and ciphers or List of unexplained sounds. The more little-known, the better. A good story is fascinating because it’s not too familiar and a good mystery even more so.
If you must go to something like Category:Mysteries which has a high incidence of entries covering likely hoaxes, paranormal events of low credibility, and so on, please try to either stick to the sub-categories that are less hokey (like Lost works and Missing ships) or proceed with extra caution.
I have nothing against a good contemporary sci-fi or fantasy story… but I’m getting really tired of stories where the author has an engaging writing style or captivating characters, but the plot depends on me seriously considering the real-world existence of fairies or unicorns or the big bad wolf. Magical thinking has its place, but don’t over-do it. (I love The Dresden Files, but ridiculously improbable things like Bigfoot bore me when it’s implied that the author believes they’re probably real and expects me to believe likewise.)
As for general writing advice, pick something you’ve never seen used before (or if you don’t, resolve to do whatever you pick better than what you’ve seen) and, as Mark Twain said, “Get your facts first, then you can distort them as you please.”