I don't have a specific site at a low reading level to recommend to you. But I have links to some relevant resources:
Check out
It's a very clear site by Caroline Jarrett with information for professionals like us.
Also, check out the work of Kathryn Summers who specializes in writing for a low-literacy audience.
One of the most important papers in this field is Kathryn's summary of a research project in which she was able to show that revising a website for low-literacy people not only helped them immensely. It helped high-literacy people even more.
Kathryn's paper is available through
or
Best,
Ginny