What about the Poor Knights Islands in New Zealand? I have read alot about diving there and its meant to be pretty darn good. Theres some stuff about the Poor Knights Islands around the net and in the book "Top Dive Sites Of The World" (I'm sure many of you have).
This is from a website I found: "The Poor Knights Islands were named by Jacques Cousteau as one of the top 10 dive sites in the world. Cousteau would know, and Cousteau was right!"
I have only done a few dives in the North of New Zealand. We were only there for a week (December 2000) and so only managed to dive on the Poor Knights and also the Rainbow Warrior.
We dived the Rainbow Warrior out of Matauri Bay not Paihia as Matauri Bay was closer to the wreck. The boat was only small and we only did a single. In hindsight we should have done the longer trip out from Paihia on the better boats with a double dive. The Rainbow Warrior was a bit reminiscent of the Tasman Hauler in Eden - about the same size and shape. The viz was pretty ordinary but it improved marginally on the wreck itself. This seemed to be fairly standard.
We did a double dive on the Poor Knights out of Whangerai and the weather was not the best. We did spend about twenty minutes on the way out to the site watching Orcas off the boat. The day we went out we went to the Middle Arch for the first and the Northern Arch for the second dive. This would normally have been the other way around but there was already a boat at the North Arch when we arrived. Unfortunately this meant we were restricted on the second dive due to reverse profiles
Both dives were really great sites. The middle arch was interesting with lots of life. We got down to about 33m at this site. The north arch was the better site but the crew limited us to 33m after the first dive. This site gets down to about 40m+ and is a dive through an arch which sits out of the water. Below the water the arch extends to become walls on either side of a very wide passage. There are lots of rays and fish swimming through the arch and the walls are covered in lots of growth. Quite an amazing dive.
As I said we only got to do a few dives but have had our appetites well and truly wetted. We will be going back for more at some stage. We also want to do some of the diving around the south island as well.
I dived the Knights alot before I moved to Oz in '91. They are a great spot with a huge amount of diverse sites. This predates the tech developments so there are probably even more sites open now.
I used to head out of Tutakaka, which is a bout an hour north of Whanagrei and makes the trip shorter. It can get quite rough on the crossing so it makes life a bit more pleasant. Tut was a great spot to hang out then too. There are alot of boats working that area that wern't around when I was there and most of the skippers I know have either died or retired so no help on that front I'm afraid.
Some of the sites I remember well were Middle and northern Arch as described, Blue Mao Mao arch (picking up a theme here?) All of which are large arches 20m+ across, with great swim throughs and drop offs. You get alot of big pleagics sitting mid water feeding on whats drifting through and heaps of life all over the show. Riko Riko cave is a nice quirky dive. A very large cavern that most boats steam into and turn around in. It's an interesting night dive and surprising the crap thats made it out there to be dumped.
Most of the knights is ledges and drop offs meaning most sites offer something for everyone. There are a few but not many sites that are newbie only Which is one of the great things. You can get a boat load of newbies but (as long as you've got a good buddy of course) You can still do the sort of diving you want. It was one of the few sites I've dived where almost every trip I'd have dolphins or Orcas swim past on at least one dive.
I guess the best reccomendation I can make is I did around 1000 dives there over the years but I'd go back at the drop of a hat if I had the chance.