I don't recall seeing an arrow discussion or I'd search it out and go post in it. Episode 8 definitely had some small surprises.
Moira called Ras'al Gul? Genius. Black Canary vs. Black Archer? However, the "League of Assassins' has a code and the Undertaking violated it? Isn't that what the league of assassins tried to do to Gotham in Batman Begins? Use an Earthquake machine to destroy the damn city?
Oliver put an arrow in Roy's leg? Hmm can't say that piece surprised me.
Earlier in the season the Black Canary asked Oliver "what happened to Slade?" We now know two things. 1) Slade survives the drug that made it look like he was dead at the end of episode 8 because otherwise Sarah wouldn't have asked what happened to him. 2) We know he dies (perhaps even at the hands of Oliver) because all of the people injected with that drug are already dead and Oliver "knows how to fight them." Incidentally I would suggest it implies a 3rd thing as well that Ivo gets his hands on the stuff because Oliver implies more than one person was dosed with it.
On to Barry Allen. Ok so we know why he was investigating this stuff. It implies that his mother was killed by The Flash. Say what? I'm sure that will be covered in his own series when it launches. Speaking of which when is that? I know Arrow fans love Emily (Felicity) but I am curious if the spinoff of the Flash will steal her?
Finally I'm curious what shoutouts and comic connections I missed this week. I saw a number of references to the particle accelerator which is more foreshadowing to the Flash, but other than that I can't say I saw much.