It is now posted: Season 8 timeline.
I've also greated a Timeline Master Post, because I was sick of not having just one post to link people to. So, if you want to check it out and/or bookmark it for future reference, knock yourself out.
Off to go update the links at the SuperWiki now... and possibly have dinner first, because it IS 11pm. (I've been having sleep/neighbour issues this week)
For those wondering about the idiosyncrasies of different seasons - I will tell you that this season ignored driving-times more than any other season has. It's like after seven years, the writers just decided to say "f*ck it!" and now Dean and Sam can make a 7 hour drive in 10 minutes. :P
Also, for anyone concerned about the large number of "unknown" dates towards the end of the season - sometimes those get cleared up when the new season starts, so it might just be a case of waiting until the fall. That being said, a lot of the time the timeline-continuity also gets super screwed up when they start a new season, so it may also get worse. We'll all just have to cross our fingers.
ETA: Also, as per usual, if you see a mistake in the timeline, let me know! I'm only human.