Community Service, The Plight of the Amazon Rainforest and The History of the Foster Care System are all examples of capstone topics. A capstone paper is a personal, dynamic project that allows a student to bring together their personal and educational knowledge at the culmination of their academic career.
A capstone project should be specific to a student's personal education experience. Different schools also have different expectations regarding length, topic options, content, etc. The chosen topic should consider all of these factors. There are many websites with sample capstone projects to get you started in the right direction. Try searching for other keywords, in addition to "capstone project," to help identify the post appropriate resources available.
Since a capstone project is personal, try to choose a topic that you're passionate about and means something to you. Not only does this make it easier to come up with resources and ideas, you are likely work on the project regularly if you care about the subject matter. You may have to present a visual aspect to your project or include an oral presentation, in which case it is wise to keep track of interesting graphics, photos and charts as you're completing your research.