I dive with sharks everyday during our dive season. The vast majority are sand tigers, but I've had encounters/sightings of 12 different species. These include nurse, black tip, white tip, hammerhead, bull, dusky, lemon, blue, mako, and a few others. I don't have my list handy - I'm like the birders. They have their bird lists, I have my shark list. It's one of my goals to dive with as many different species as possible.
The hammerheads I've seen are by far the shyest. With them is usually only a quick glance. The opposite end of the spectrum is the bulls and they've provided the scariest encounters. On more than one occasion I've had a bull circle me and get in my face with an agressive posture. Yelling and blowing air in their face from a spare second stage seems to discourage them, as well as, becoming agressive yourself and moving towards them. A good hard blow to the nose from a speargun butt, a dive hammer, crowbar, or whatever you have handy, seems to work well too.
The sand tigers are just there. They're curious and will come check you out occasionally, but mostly they could care less about you being there. Unless, of course it's breeding time and you're among a bunch of males. They will get very close trying to figure out if they can mate with you. They remind me of a bunch of human males in a bar when it's getting close to closing time.
At any rate diving with sharks is an exhilirating experience that, despite having done it hundreds of time, I still get excited.
If you're interested in diving with sharks, I'd definately check out the Hatteras, NC or Moorehead City, NC. I saw the show the Discovery Channel list came from, and I had to laugh at some of the locations. We put a lot of them to shame as far as the number and size of sharks. Plus you'll be diving historic shipwrecks to boot.