all are doing money making schemes through SEO
so better go with Youtube for some free knowledge
as well free SEO articles are there in the Blogs
And forums will make you to pay for some useless tools or services
Well, highranking would be one of the best and reputable forum sites out there.
Digitalpoint and warriorforum too.
On the other hand, if you want to stay up-to-date with what's happening in SEO world then make it a habit to read MOZ and searchengineland.
They also have this Q&A community where you can ask questions.