Or S2E3 if you prefer. I'll edit this post after it airs because at the moment it's not 100% certain what they'll air, but it's pretty much taken for granted that it'll be part 2 of Endless Eight. As I mentioned in the general Haruhi thread, there's a live stream that's (supposedly) going to have English subs. Haruhi will start, according to the Japanese guy whose stream it is, when at 1AM Japanese time.
(Stream removed because the episode is over now)
Then afterwards (or instead, if you miss it) look in these various places for subs:
http://a.scarywater.net/afk/ (I think they tend to be the first ones usually).
http://www.nol888.com/plog/ (Does HD versions but many, many days after it airs - still waiting for Endless Eight part 1.
Edit
OK, I've just seen the episode. About the only thing I can say without spoiling anything is that I've noticed how the series tends to only be able to relay the plot via long conversations; it can't seem to have the plot conveyed through action, movement or any sort of interaction outside of sitting down and talking. You can almost hear the gears change as it goes into Plot Mode.
Anyway, spoilers follow:
First of all, this will apparently be a three-parter.
The first half of the episode was the repeat of the events last episode. There were many nice little touches, like how Yuki bought a slightly different mask this time.
It was nice how they actually re-animated the repeated scenes rather than just lazily copy-pasting them across. Everyone in the stream was very impressed with Haruhi's tits and her sexy Chinese dress style swimming costume (which you can't quite see fully in this image).
Itsuki bowling made me laugh. He looks almost as silly as Peter Crouch.
Edit 2
There's a torrent of the stream. It's going to be pretty bad quality (it's about 40MB) but it might be worth checking out if you really want to see it.
Link
Edit 3
Mazui subbed Ep 13 - XviD
Mazui subbed Ep 13 - h264 (better quality)