Probably the hardest part about starting a writing project is coming up with a topic. There are thousands - even millions - of places to find information, but without a focus for your project all of that is not too helpful. Your first step, then, is to try to narrow down your topic a bit. Look through some of the following resource sites.
This site is a search engine search designed to help you depending on what step of the process you are in. Are you looking for a topic, or do you need to redefine and narrow your topic? Try this site first and explore several different places.
The next two sites are organized around topics that you might be interested in. Browse through and try to come up with some ideas. The VLRC Directory and the a list of Hot Topics.
Another option is looking through Teen Ink, either online or in class, for topics that other high school students are writing about.
By tomorrow, you need to post an entry to your blog that deals with your efforts to find a topic. What are you going to write about? Why? What made you come to that decision? What was your thought process? What resources did you explore to help you come to that decision?
In your posting, remember to include a hyperlink to any sources you mention or cite. Make your links part of your sentence writing, as I do above. Good luck.