One of the funnest articles I've read on the now famous pound symbol was called "Ode to the #Hashtag: A tribute to the most ubiquitous symbol of our digital times." It was written back in 2013 by Andrew Miller on Medium, but is every bit as relevant today as it was back then.
What is #MobMin?
The Twitter hashtag #MobMin is a collection of resources to help you learn more about integrating mobile technology in your ministry.