There are also mailing lists. These are registration sites - join the list and you are put into an email database. Every message that is sent to the list is forwarded to you. I am listed in six of these. I have received one message in the last three months from one group and at the other extreme, I sometimes get 20 messages a day from another. Some lists are very strict about what messages you can send (i.e. genealogy only), others are very lax and the members post day to day information about themselves, tidbits of information on just about anything, or URLs for informative sites.

Most of my lists are through RootsWeb

You will also find some at Yahoo where they are called Groups.