As an event manager I use Instagram to capture images of my events live, using those images and pushing them out to the various social media mediums Instagram offers. I also use it as a kind of image database that I can refer back to if I am looking for inspiration or to look back through if I need to remember how I themed a particular event.
Using Instagram offers the ultimate in user engagement, real-time. By adding a unique hashtag to your shared image, you can create real-time conversations. By doing a bit of research before your event, you can see what the current trends are in hashtags and find one that suits your event, by doing so, attracting even more viewers to your account whom are simply following that hashtag.
Here is a really informative blog on the Eventbrite site with some great tips on using Instagram for your events!