School is over for 2011-12 so I guess you had to figure out something yourself. Sorry that we were unable to get back to you sooner but, hey, you may have learned more by finding a project yourself. I hope we can serve you better next time however.
It has been over two weeks since you asked your question, so I hope this is not too late to help.
If you havn't already, read the EDUCATION.COM Science Fair Help
They've checked with the experts, and have gathered the information to ease the stress of science fairs for everyone. To find a good project look at Science Fair Project Ideas - you can use this drop-down menu to browse projects by grade and/or specific subject area.
Some very helpful and FREE sites for project instructions are Science Fair Sanity and FSFP Free Science Fair Projects. I have included their links below.
Elementary school students can download free science fair project ideas on ScienceFairSanity.com for grades 3-6.
FSFP free science fair projects may be one of the best resources on the internet for your science fair project. Select your school grade and take a look at the examples of real completed projects.