People are gravitating towards SBNation blogs and forums. They aren't always the best, but they are often the most active. The quality of content varies wildly. Also, the fan bases vary even more wildly.
e.g. (SBNation blogs)
Timberwolves - knowledgeable but casual
Lakers - clueless and casual, but big numbers
Denver - clueless but passionate
Celtics - knowledgeable and passionate
Portland - knowledgeable and passionate
Memphis - knowledgeable and passionate
Houston - passionate, but clueless
Sacramento - passionate and somewhat informed
I've trolled enough of these to know.