The other day, I had an idea. It occurred to me that daily horoscopes - the traditional kind - might not be as useless as they seem at first glance: They usually give, or at least hint at, suggestions for specific things to do on a given day, which can be a useful cue, allowing the user to put less effort into finding something useful to do with their time. They can also act as a reminder of important concepts, rather like spaced repetition, and have the possibility of serendipitously giving the perfect advice in a situation where the user would otherwise not have thought to apply a particular concept.
This seems like something that many people here would find useful, if they weren't so vague, and if they were better calibrated to make useful suggestions. So, after getting some feedback, and with the help of PeerInfinity (who did most of the coding and is currently hosting the program), I put together a tool to provide us with a daily 'horoscope', chosen from a list provided by us and weighted toward advice that has been reported to work. The horoscopes are displayed here, with an RSS feed available here. Lists of the horoscopes in the program's database can be found here, with various sorting options.
One of the features of this program is that the chance of a given horoscope being displayed are affected by how well it has worked in the past. Every day, there is an option to vote on the previous day's horoscope, rating it as 'harmful', 'useless', 'sort of useful', 'useful', or 'awesome'. The 'harmful' and 'useless' options give the horoscope -15 and -1 points respectively, while the other three give it 1, 3, or 10 points. If a horoscope's score becomes negative, it is removed from the pool of active horoscopes; otherwise, its chance of being chosen is based on the average value of the votes it has received compared to the other horoscopes, disregarding recently-used ones.
There is still a need for good horoscopes to be added to the database. Horoscopes should offer a specific suggestion for something to do that will take less than an hour of sustained effort (all-day mindfulness-type exercises or 'be on the lookout for X' are fine) and that can be accomplished on the same day that the horoscope is read. Horoscopes should not make actual predictions, but may make prediction-like statements that are likely to be true on any given day, like "you will talk to a friend today". Horoscopes can be submitted here, or left in the comments. EDIT: Any comment anywhere on the site that contains the phrase "Horoscope version:" or "Horoscope:" should now automatically be emailed to me, so feel free to horoscope-ify new posts in their comments, unless this comes to be considered spam.