Scripts in PHP about math subjects. Some math problems lend themselves quite easily to a solution in a general-purpose scripting language such as PHP.
For other math problems, you are better off with specialized tools.
One tool that I extensively explored in 2013 is the computer algebra system maxima. I wrote quite a few scripts for it, in response to questions on the Google+ Mathematics community, and I published them there, if you are interested.
I have always thought that Social Media are not that particularly useful for any specific purpose. When on top of being almost useless, someone tried to impersonate me, I closed the door on Google+. Here he is:
I think that Facebook, Google+, and LinkedIn are even dangerous.
If anything of financial value ever starts going on there -- as opposed to just aimless babbling -- you will soon no longer be talking to the person that you think you are talking with at Google+, Facebook, or LinkedIn, but more likely to his murderer, who has successfully taken his place, and is now controlling his social media accounts.
Stealing passwords is excessively easy, especially from people who use Windows or from people who use typical consumer-oriented routers that generally have backdoors. You can find a few of these backdoors here:
Facebook and Google+ dangerously give the impression that you are talking to the person that you think you are. Especially the images (avatars) are very misleading. The accumulation of history also gives false credibility. None of this will help, if the attacker manages to get control of the account. He will start leading your life in your stead. Since you are at that point just an annoyance and could disturb your attacker, it would be more convenient that you disappear.
I no longer use Social Media that insist on real names and encourage you to spread around pictures of yourself. Throw a bank account with money into the fray, and half of the members of the community will sooner or later end up with their dead bodies concealed in concrete somewhere in a nearby construction site.
Money will inevitably become a more prominent part of the social interactions in Social Media. At some point along the way, these Social Media will silently start morphing into fully-fledged assassination games.