Actually a couple of ways to do and pick whatever is the best for that day. okpay -> btc-e is one way though.

The trick is getting the money out.

From what I have read the arbitragers were using dwolla to transfer between MtGox and BTC-e

Just in case you weren't trolling and because we have a lot of new people on the forum, I'll share some pro tips to deal with slippage on both sides.

For people who have no idea what he's talking about, lets say he has 100k USD he wants to use to buy Bitcoins. The price is at $118. If he puts in a market order for 100K, the order will end up buying coins at $118, $119, $120. So instead of getting in at $118, he's in at $119+. The ticker says $118 but he's forced to pay $119 to get back in. So that sorta sucks.

You only want to use market orders when you want to push the price up or down. Sometimes you'll pay the extra when buying (from slippage) because people will see a big purchase, more people might start buying, you move the market slightly higher, maybe start a rally, there's some built in short term protection for your BTC. When you market sell, you push the market a little lower and sometimes get panic sellers to join in. If you're not trying to move the market up or down you really shouldn't be using market orders.

But now you're thinking, I don't have all day to spend my 100K-500K USD on coins, I have shit to do. Fuck slippage, I want to get back in the game quickly. There's another option.

You want to place fairly big bid/ask walls near the edge. Preferably, right on the edge. The reason these walls get taken down so quickly is because the other side is also concerned about slippage. A 100k bid wall right on the edge, means people on the ask side can sell a bunch of coins with no slippage. Normally selling a bunch of coins you'd end up selling coins at $118, $117, $116 as you worked your way down to fill the order. By putting the wall right on the edge, you're letting everyone know they can buy/sell a fairly large amount and not have to deal with market orders (no slippage).

So if you're buying/selling a large amount, break it up into a few decent sized walls, put it right on the edge, they will get taken down (filled) very quickly. You can get in with your 100k USD right at $118, giving you a little lower price point. I see a lot of people getting impatient, forcing themselves in at a higher price when it's really not needed. You don't have to stick to limit orders $1-$2 below the ticker that can sometimes take hours to get filled. You don't need market orders. Go to the edge, get back in when you want to get back in, and go from there. You save time, get in more quickly, and sometimes the timing of when you get in is more important than the price.

In wonkytonky's case, a few bid walls right on the edge would have gotten filled extremely quickly, and slippage would never have come up. If anyone has different strategies they use to get in and out with large orders feel free to correct me.