I built a very accurate value estimator for properties en Amsterdam for the sake of it. Then put it here amsterprice.com . It is slowly starting to pick up, but as itnis for free I am only watching hosting bucks go. Still proud of it! :)
How about this. A crossword puzzle generator. The user enters a keyword, a person's name, or a date, and your program generates themes, words, and clues associated with that prompt in the newspaper archives. So for example, if I enter the keyword "Trump", your algorithm does some word-association magic (I'm not big on the terminology when it comes to text data) and comes up with a bunch of words and clues drawn from your paper's archive of writing about Mr. Trump...