Frequent dancing causes a 76% reduction in the risk of dementia. The benefit seems to be from freestyle social dancing, though I don't think that part is as well-verified. The benefit seems to be from making large numbers of quick decisions.
I wonder if playing jazz has similar good effects.
For something a little geekier, Shiva Nata, a system of keeping the mind fresh by doing more and more complex movements. The author of the blog is a silly person, but the system seems to be for real.
Edited to correct html which was entered in the text field instead of the html field. It wouldn't surprise me if having to deal with electronics and computers tends to prevent dementia, considering the number of fiddly and changing details one has to deal with. Or is fun required?
I see in a reply of yours that you're interested in salsa dancing. By far the most important factor in getting better is to quickly achieve a level of competency that makes salsa socials really fun. I don't think I've gone more than 7 days in the last 2.5 years without attending a salsa social, and this has been the biggest factor in my improvement.
You may already be at this stage since you said you enjoy dancing, but if not I suggest you learn the basics from a friend or a class (I would spend no more than 10 hours on this stage), and then force yourself to attend a bunch of salsa socials, until you start really enjoying the experience.
Once you've reached this stage, you've solved the motivation problem, and now you can optimize towards becoming a really good dancer (if you even want to at this point - it's not necessary to reap the majority of the benefits).