Page Strength
SEOmoz's Page Strength offers a way for you to gauge the impact of your own site. It can be a domain or a specific site like a blog inside the domain. I checked it out for my own blog and scored a 4.5. Hurrah! My children's lit blog scored slightly higher at a 5. Of course, you can't just leave it at that, you must see how other libraries in the area score, and how larger sites like ALA score (9). It is a lot of fun, and perhaps a bit addictiing.