Many libraries review, collect, and organize material into subject guides so it may be more easily found and used for research. Below are two examples.
(web.mel.org) If you look at the bottom of the left hand sidebar you'll see links to subjects. The material selected for inclusion has been reviewed by librarians and is often annotated. MeL has a Michigan focus.
(kidsclick.org) KidsClick! was created by a group of librarians to guide their young users to valuable and age appropriate web sites.
Other excellent library subject directories: Internet Public Library
(ipl.org), and your local
library website may have subject directories to local information.