Take a look at Wolfram Mathworld - an online encyclopedia of mathematics- in which you can browse areas of mathematics, look through the alphabetical index, or search for a specific topic of interest.
Googling these phrases actually yields some interesting results...
thesis topics mathematics - leads you to the websites from several mathematics departments who provide suggested topics for their students.
mathematics senior theses - will retrieve lots of links to the online collection of theses from other universities. Look for those that are specifically undergraduate theses and see what kinds of topics they wrote about.
Try searching Tripod for one of your interests and mathematics. For example:
Baseball AND Mathematics
Evolution AND Mathematics
Elections AND Mathematics
Review the results and see if anything sounds interesting. Take a look at the table of contents and/or the index to see if you can connect to a particular hypothesis or theorum.
We also have a number of books that are popular treatments of mathematics, such as:
*** Browse the full list of popular math titles ***
Some of the topics or chapters in these titles may spark an idea for your paper.