You might not want to be a full-time art teacher or professor, but there are plenty of opportunities for teaching art, either as a one-time deal, or on a part-time or occasional basis. While art can be a difficult thing to teach, it can also be fun and rewarding depending on the type of class you teach, the age group and level of skill of your students, and your own experience.
A few years ago while I was attending art school, I got a seasonal job teaching a youth painting class at a comunity centre. I decided to base my curriculum loosely around a painting class that I'd taken in my first year at university. I was amazed at how teaching a group of teenagers the same things that I had learned at school helped me to practice and remember those lessons and skills even better than I had the first time around.
Teach Something you Enjoy
If you are a painter, teach painting. If you're more of an art historian, teach art history. It seems obvious that you should want to teach something you know and like, but remember that, unless you are applying for a job as a college professor, you don't necessarily need to know everything there is to know about a given subject in order to teach it. Teach something that you want to learn more about! If you are in charge of a group of younger students, chances are that answering their questions and trying to explain things in a simple manner will help you learn more than you knew before.
Find your Own Style
If you get stage fright easily, the idea of teaching a group of people can be daunting. If you simply can't do it, there are opportunities for being an art tutor - teaching one-on-one, often in the pupil's home, might be a little easier. You can treat teaching as a bit of a performance, getting up in front of people and reciting your lesson, but don't forget to be yourself as well - make the class a conversation between you and your students, answer questions, and be approachable.
Everyone's had to take that one class where the entire group - including the teacher - seems bored out of their mind with the subject matter. I know it's hard for me to learn anything useful when nobody seems interested. Sometimes all it takes to make a subject interesting to others is to show that you're interested in it. Have fun, make a few jokes, it doesn't have to be completely dry and academic to be useful.