SUMS is a mathematics symposium organized by undergraduates in the math department and held in Spring every year. The topic is different each year, and is pitched and decided by the organizers at the start of the academic year. We are always looking for more help organizing, so if you are interested, please send us an email at aren_guralp [at] brown [dot] edu. We also have a dedicated website.
Past themes have included:
Math and Language
Math and Puzzles
Math and Illusion
Math and Thinking Systems
Math and Visualization
... and others!