August is a great time to get a lot of application work done. Once school starts, you will have homework and extracurricular activities on your schedule as well. Applications take more time than you expect and colleges can tell if you threw yours together at the last minute. I like to say that applying to college is like adding an AP or advanced course to your senior year schedule.
Take the time now to fill out demographic information (your name address, etc), and start writing some essay drafts. Many students think they can just think about an essay and it will magically come together. I have found that sitting down and writing out many of your ideas will result in essays that are more cohesive.
Also, it takes time to remember all of your activities and to describe them meaningfully in the small amount of text space provided on the application.
If you are applying to state colleges and universities, make sure you are filling out applications for the year 2015-16. Some universities do not have their application available until September. If it is not clear, please call and ask them. It's no fun to fill out the application twice.
If your family earns a lower income or if you are on the free or reduced price lunch program, talk to your school counselor about fee waivers. Fee waivers allow you to apply to colleges without paying the application fees now. Some colleges defer the fees and take them out of your financial aid award when you arrive on campus. Most counselors will be back in the office at the end of August, but will be swamped the first few weeks enrolling new students and working on schedules. Be patient!
Good luck! Enjoy August!