I think you'll find what you're looking for here, both lighthearted and more serious discussions on the motives, what ifs, etc. I found that looking for discussions in the search the forums thing lead to a whole lot of information. Plus, even better, there are some really knowledgeable members here.
Any favorite characters that you like to speculate about?
Welcome and while I can honestly say I myself have little taste for speculation. You will be happy to find that I am in the minority here and that you are in the majority. There is much discussion about what ifs, where tos and what thens, all backed up by pertinent facts. Yes this is a fine place, a bit lonely every now and again but nonetheless a wonderful site. Have fun and remember, "not all those who wonder are lost."