To make your project accessible to an audience of students from varied disciplines and departments, consider selecting a theme that integrates math with other sciences, social sciences or liberal arts subjects. For example, you might look at the mathematics guiding the experimental "Oulipo" writing group, largely comprised of mathematician-poets. If your interests lie in environmental studies, you could use mathematical models to assess a local ecological population.
If your studies in mathematics focus on statistics, select a project that draws on current issues or trends related to student life. For example, you could measure student opinion about some change on campus, such as a new policy related to dormitory life, a new student union building or new dining hall options. Look for unusual and complex angles to your statistic gathering, considering the demographics of the students you poll, how opinions change over time and how opinions may change based on how you ask questions.
Don't limit your presentation to the basic tri-fold poster. Particularly if you invite grade school students or the general public, your presentation will benefit from a dynamic and interactive "hook." For example, you might create a three-dimensional model of a mathematical concept or a computer simulation that shows any functions of movement, development or growth. Whenever possible, look for ways that your audience can interact with the display.
To enrich your math project, consider working with a student from another discipline, either within mathematics or in another field, entirely. Through collaboration, you may find a new perspective helps you to solve a problem within your own discipline in a creative new way. For the presentation, divide your display to reflect each of your approaches. Pairing with a music student, you could study decibels or the production of major and minor chords. Working with a computer science student, you could focus on global positioning systems, or GPS. Working with a history student, you could focus on mathematical models of past ages and use them to solve modern problems.