What are some ways a woman can defend herself?

I'm not even really sure which category I should put this in, but here lately I've been kind of paranoid about my safety. I'm not really comfortable where I live, and sometimes I do worry about intruders. What can I do to protect myself if someone should break in? And what can I do if I'm out and I'm attacked? Any ideas or suggestions would be helpful. If those situations should arise, I would like to know if there's anything I can do to help protect myself. Thanks.