Here are some links designed to help you with science fair projects.
#1 Suggestion: Make sure your topic is a true experiment, not just a demonstration. Unfortunately, there are MANY library books with titles such as "blah blah blah Best Science Projects for Children" that are NOT true experiments; they include many demonstrations.
A good science FAIR project will have a title such as
"How Does __ ___ ___ affect the ___ of ____?"
Once you have decided upon a topic, be certain that you RESEARCH your topic. This aspect is often what separates the winning projects from the others. And, don't worry if you don't find research that matches your topic exactly; you need to learn some background information on your topic, and exact-matching research may not even exist on the web at this point!
Please try to be more original that simply comparing two products of the same type. These projects have been way overdone in recent years. There have been plenty of "What's the Best Paper Towel," "Pepsi or Coke?"
Not everyone will find an EXACT topic from all of these pages; what I have always told students is that this will help you start thinking. It's really best if you come up with your own idea, (often related to something you see on these pages) and that it's something in which you have a true interest. That makes the project more enjoyable!
NOTE: Links were checked as of 9-13-18 . Many of the sites that have lists of other sites lead to broken links; several of the webpages were made a few years ago and have not been maintained.