Question: I would really like to find a way to show college admission committees my interest in philosophy and history. I know that many students who are interested in medicine or in other scientific fields do internships and research projects in order to show this interest. Are there similar opportunities in my fields of interest?
If you live near a college or university (and almost everyone does), try contacting several professors who teach courses in history or philosophy that sound interesting to you. (Course catalogs can be found online and usually list the name of the instructor. You can then go to the college's online directory to get the prof's e-mail address.)
Once you'll culled some names from the college Web site(s), then write each prof a brief note explaining your interests and aims. If you're not expecting to be paid, you'll be a lot more attractive to professors than if you're looking for a salary. You can volunteer your services for whatever research-assistance or other (even menial) tasks that the professor requires.
Alternatively, many cities and towns--even small ones--have historical societies, and this might be another place to look for opportunities.
One of the best ways to express your passions is to dream up your own project. Is there a particular topic you'd like to research? You don't need any formal affiliation to do so, but if you think it will look more "official" to have a sponsor, see if a local teacher, college professor, historical society officer, librarian, etc. will oversee your endeavor.
College admission officials are often more impressed when a student pursues a passion independently than when he or she joins an organized program. So don't be afraid to strike out on your own. Write a research paper, make a film, begin a book ...
You'll have to take initiative but the results could be very fulfilling.
Finally, if you've got money to burn, you might want to check out this internship program: http://www.petersons.com/summerop/sites/inc/020372so.asp