There are now 230 Cortana Skills in the Windows Store, up from 174 in October, for around 30% growth over the last two months.
Microsoft says Cortana has more than 145 million users (in July 2017) which is a pretty large installed base, and I am sure 95% of our readers have Cortana at least on their PC.
I have however not even tried to add any skills to Cortana, and I suspect most of our readers are in the same boat, which I think is somewhat neglectful of Microsoft followers who should, after all, provide the initial active user base which would pull in more developers.
If you are a Cortana watcher I would, therefore, suggest having a look at the 230 skills currently available and see if one or two could find a useful home on your PC. I am sure the developer and Microsoft would both be thankful.
See the collection here. (US-only at present)