Yesterday I received an email from a listserv that I belong to regarding the use of Slideshare for research. This email reminded me of some good advice I found reading through the Buck Institute's book PBL in the Elementary Grades. The book suggested using Power Points found online as resources for lower level readers. Of course you would want to preview these to be certain the information is correct and appropriate, but there are really a lot of good Power Points on the web to choose from. I did a quick search for Wisconsin invasive species in Slideshare and found one that was done by a UW Madison scientist which would have been an excellent resource for our third graders when they did their Invasive Species PBL last year.
Some other ways to find websites that are easier to read include using the Advanced Search feature on Google. When doing a Google search, on the bottom, left side you can find "More Search Tools". When you click on that, you can select reading level. Sweet Search 4 Me is a search engine geared specifically for elementary students with every web site evaluated by their research experts.Twurdy is another search engine that rates its articles by reading level.Teaching students to "read" pictures can also provide them with some of the information they need.
In Wisconsin, your local library card will gain you access to Badgerlink, which includes the Elementary version of Encyclopedia Britannica. The articles in this encyclopedia are easier to read and also allow the viewer to listen to them. Some schools have direct access to Badgerlink when at school. Finally, check with your school's librarian to see what resources are available through your library catalog. Ours lets us search for both books and online material by reading level. Hopefully at least one of the above suggestions will help you support all reading levels in your classroom.