A directory site lists sites you can use in instruction. A directory site may be enhanced by original content, but mainly is a links collection (but not solely lesson plans).

A Lesson Plans site has a collection(s) of lesson plans &/or links to lessons and units.

printables, clip art, instructional aids

Explains liserserv,
chat room; blog;
instant messaging
Examples of each.

Popular reference sites not specific to education, such as: newspaper, dictionary,
weather