Academic discussion lists are a tremendous asset to the online researcher. They differ from discussion groups in that an automated program manages discussions and sends them automatically to subscribers only. The most common discussion list is called Listserv. You can subscribe to a Listserv about a particular topic, then unsubscribe when you want to. Discussions are delivered right to your email box, usually daily or weekly. You can post your own questions as well--just be sure to consider the credentials and authority of your respondents. While Listserv contents are generally more serious and authoritative than discussion groups, there is always the danger of misinformation being posted.
To find a Listserv on your topic, check out Liszt, a directory of mailing lists that is searchable by keyword or by category.