Key Largo. You've got reefs that are 25ft deep for the new divers that offer cool stuff for the experienced diver as well. Saw my first bull shark there at French Reef back in January. Cool dives for both.
1. Molasses Reef - Offers up some large grouper, schools of cudas, etc. Haven't been impressed with the macro there but for schools of fish its tough to beat.
2. French Reef - Same kind of things as Molasses.
3. Wreck of the Benwood - With the deep end at about 50ft the Benwood can be accessed by all skill levels. Offers up some larger schools of permit, jacks and don't forget to look under the hull for a large grouper and lobster. Lots of little nooks and crannys to investigate small stuff.
4. Christ of the Abyss - This is a statue of Christ. It is a great dive or snorkel. Its in 25ft of water, makes a great photograph and is accessible to even snorkellers.
5. Pennekamp State Park - Pennekamp isn't the best dive operator and I've had a couple of experiences I'd rather forget but the park is a great place to visit if you've never been. They have a roped off snorkel area with a 17th century spanish galleon sunk right there. The only real thing left are the canons and anchor but still pretty cool. Great place for small kids to dink around. The only positive about the dive op is they have the largest boats and are easy to find amongst the armada of boats when you surface. They also have a cool canoe maze through the mangroves that's a lot of fun.