Responding to other people's posts allows for a soft sell of your own products and services while being helpful and providing solutions to their concerns. I often gently make reference to my publications or services. It might seem to take a little longer. It is a very effective way to go much further, though. Referrals come when and from where you least expect them, I have noticed.
Online newsletters are like hard-copy newsletters.
The two differences I am finding are that online newsletters appear more willing to accept articles and that the decision-making process on acceptance seems faster. The online newsletters often have a larger subscriber base than many hard copy newsletters. For me, this has also been like trying to eat only one potato chip. The emergence of online newsletters is huge. Finding one generally leads to more.