I can't really offer up any 'message board' type sites for discussion and theorizing. I kind of flit about according to core queries or topics. I have found some interesting things here and there, to do with whole topics - humanresonance.org was very interesting for a scan through whilst looking for some particular information, and I go back now and then to try and read through all of what they have on there - and that seems to be the easiest way of being lead to something else.
But one definite thing I have found is that one should not be limited to English sites. If one wants to go as close to a source of information or topic as one can, country or region where this one thing is prevalent should be searched out, with the use of a translator.
Someone once showed me a cool French site to do with UFOs over there, and to think that I would have completely missed that by sticking to English sites!