In the cities I've lived in, there have been quite a few hackathons put together with other industries such as Hacks & Hackers (Journalists and devs) and Music-related hackathons. Take a look on meetup.com, there are probably tons of other types.
There's also Comedy Hack Day [1], my personal favorite hackathon(s) of all time. I've been to 4 so far and have flown across the country just to participate over and over again.
Now that I see it in the spotlight. I wonder what other kinds of niche hackathons do you guys know about?