Former colleague, and well known author and educator Dave Taylor has put together a site that should be useful to all authors. The site performs a number of standard readability tests, including the fairly well known Kincaid and Flesh forumulas, against a submitted URL or Word document. The results allow authors to quickly evaluate if their writing level is appropriate for their intended audience and can also provide useful insights to readers as well as authors. One interesting exercise is to evaluate your site and then compare the results to some of your favorite sites.
As Dave says:
Curious about how complex your documents or Web pages are to read? You don’t have to get a team of experts to study it: you can just use readability.info to analyze the characteristics of your writing and ascertain a readability score. By comparing the readability score of different documents (or Web pages) you can better hone your writing and make sure that you aren’t creating overly complex sentences and paragraphs for your audience.