So I am sure many of you have noticed some of these effects, which have happened since Starcraft II has come out, but I urge you all to take advantage of them because who knows how long they will last.
Wintergrasp: On Llane horde has been winning the battle at least twice as often as they have been. This is a great chance to get kills, honor, and of course VoA in. Of course on some servers the opposite might be the case for you. If that is case you have to plan out how you are going to accomplish all the tasks above with less time to do so.
Battlegrounds: I haven't gone in to test it, but a lot of the standard players will not be there meaning the frustration level may be higher than normal.
Gems: The supply has stayed the same, but the price has gone up by a significant amount. This is probably do to the fact that the gem sellers don't have the competition of the random undercuts and still have the supply to deal with the current market demand.
Enchanting Mats: Prices have gone up, but supply has gone down by a large amount. With less people on WoW the huge influx of enchanting mats is seen through not as many randoms being run. I urge anyone to take advantage of this as you can sell these mats for, at times, triple the current worth. I have a feeling this weekend a couple could even get to 4 to 5 times the normal price, most likely dream shards.
Saronites: Price has gone up by a large margin, but keep in mind the demand is much less. So don't use all your frost badges expecting to make a huge profit because you might be stuck with them since not enough people will actually want them.
Others AH Items: There are many other things that supply and demand is off for at the moment so take a look through the AH and see what is going on. Keep in mind also when you post things the buyer base is not going to be as high so over posting is going to cost you a lot more.
Leveling Professions: Horrible time to do so. Mats are overpriced and not being farmed as much as they normally are. This means the time invested and gold invested is going to make it not worth the hassle.
For The Horde: Gauss won't be running this on the weekend because of the lack of people and maybe more so because I will be playing Starcraft II.
So those are just some things to keep in mind and take advantage of if you can. Things won't get back to exactly how they were obviously, but the longer Starcraft II is out the less of an impact things like this will have.