Also, what you get out of a list often is related to what you put into it. Some people avoid discussion lists because they are concerned about receiving too much e-mail. The amount of e-mail being distributed over a list varies greatly from list to list, depending on the number of subscribers and how often they post messages. Join one list at a time. You can almost always unsubscribe from a list if you start receiving more e-mail than you would like.
Most lists send instructions on how to unsubscribe with an initial welcoming message.
So, it is best to keep the first message you receive from the list host. In many cases, you can also choose to receive messages from the list compiled into one larger message per day or per week. This site claims to list 90,095 mailing lists. This leading manufacturer of list software has a search feature on their home page for locating lists. This directory site allows you to search for newsgroups and provides archives of newsgroup discussions.