There are tens of thousands of these newsgroups. Subjects like law have dozens of sub-specialities. You can ask questions, pose hypotheticals or respond to questions others have posed. Thousands of very educated and motivated people read these questions, so you stand a good chance of getting a very informed response. In fact, you will probably get lots of very informed responses.
Mailing lists are very similar to newsgroups.
Again, there are thousand of mailing lists. You subscribe to the ones you want. The difference is that every single email question, response and comment which is posted to that mailing lists is sent by email to every subscriber on the list. Subscribe to a couple of active mailing list and you will find yourself with a couple of hundred email letters in your mailbox every time you logon. Pick and choose carefully.