Quora.com and goodreads.com have been popping up more frequently in online meanderings over the past couple of weeks. Quora is basically a question and answer site, but not in the sense of querying Google or Wolfram Alpha. It's not a search bar that spits out answers; Quora is to Google is as an essay test is to multiple choice. The answers returned are ostensibly from "experts," but anyone can pose a question or answer. Just try to know what you're talking about if you submit an answer, for the sake of the other users.
Goodreads is a place to discuss works you have read, or are reading. It's got the requisite user-populated bookshelf, where you can add the titles that you have read, are reading, or would like to read. Like Quora, users can pose a question, or "explore" works, among a group of other readers. You may be "friends" with someone on the basis of their having read the same book that you are reading, or you may choose not to be friends with anyone. In any case, the book explorations/discussions can quickly shoot off onto tangents expected or otherwise, with hours or days passing between contributions by others. It's great!
What struck me about each of these (I believe I stumbled upon goodreads.com from a Quora question somehow, but I'm not entirely certain of that) is the quality of the communities. There don't seem to be a large number of users yet, although Quora is gaining traction, but those who participate do so with thoughtful effort. These discussions encourage thought and introspection, which can only advance the attempt to know thyself.