ASOIAF University is a great blog created specifically for being an unbiased compilation of any and all meta and theories circulated through the Tumblr blogosphere, and it also includes outside reviews and interviews here and there for further interpretation of the ASOIAF series. Some of them are amazing, well-written and well-thought out, some are argumentative and heavily opinionated and spawn debates (usually in the form of the show versus the books), while others are just short opinion pieces; some I agree with, others I don't, but regardless all are quite fascinating to read. Anything focusing on character complexities and motivations and the prophecies within the series itself is always an intriguing read for me, personally speaking.
Along with such places like popular theory pages or discussion forums, all are fantastic to see the various thoughts, opinions and theories from fans. I just really love meta, you guys.
(NOTE: For anyone who only watches the show and hasn't read the books or doesn't have any knowledge what happens beyond the show itself, be forewarned that there are massive spoilers in these places, the first one especially since some posts don't even bother to have entry cuts. In fact, if you want to remain spoiler-free I strongly advise that you don't go to these pages.)