Shore diving in Maui.
The visibility nearshore obviously will not be as good as out at Molokini, and most of the time the viz at Lanai will also be great because there is so little runoff from that island. But shore dive has a few advantages, such as being done whenever you choose, and being CHEAP.
A pretty good guide to the main snorkel and dive spots is the free brochure/magazine "Maui Dive Guide" that you will find sitting on the counter at the various Maui Dive Shop branches. While the book "The Divers' Guide to Maui" by Chuck Thorne has info on many more dive sites, it doesn't add much info on the popular sites beyond what is in the Maui Dive Shop free guide.
DIVE GUIDES
There are lots of instructors/DMs that will take people on guided dives. I'll just mention two.
Shaka Doug here on scubaboard is a guy with a lot of aloha spirit and the unique "scuba bus". If you are driving down the road and see a bunch of bubbles floating through the air, you'll probably find the scuba bus a few cars ahead of you.
Welcome to SHAKA DIVERS Web Site!
The dive shack in the Sheraton, right at the base of Black Rock does guided dive.
-----------------------------------------
SOUTH MAUI
Going on your own, the best spot to start in S. Maui is
Ulua. Easy entry. Easy navigation. The main problem is limited parking that fills up with beachgoers and snorklers, typically before 10AM.
Makena Landing is the other very popular spot in South Maui. Also called 5 Caves; 5 Graves; some snorkel boats also call it Turtletown; and just to be extra confusing some call it by what you find on nautical charts ---- Nahuna Point. The initial swim out is a bit longer than Ulua, but again the navigation is very simple -- keep the reef/rocks on the right going out, on the left to get back.
WEST MAUI
Kidspot can supply better info, since I rarely bother to make the trip over to west Maui.
Old Airport aka Kahekili Beach is a popular dive training site for West Maui (as is Ulua Beach for S. Maui). Lots of stuff to look at even though the reef doesn't have as much vertical relief as does Ulua. Basically you go a few 10's of yards into the ocean, and then swim along the reef parallel to the beach.
Black Rock is an interesting dive, but it can involve long walks to get to the entry point. One strategy is to drop all of the gear off at the golf course just to the north side of the Sheraton. Go park the car and walk back unencumbered. Then gear up, a short walk across the golf course and you can enter on the north side of Black Rock. You exit point is about 45 minutes away, on the South side of Black Rock. Average depth 30'. No exit in between. Because of this, the Sheraton dive shack normally does an out-and-back from beach on the South side. This is a great spot for a night dive.
Another very popular spot on the west side is Honolua Bay. Well north of Lahaina. During the winter swells this spot is also a popular surfing spot. The best surfer viewpoint is at the top of the hill just beyond Honolua Bay. Honolua bay is good for both diving and snorkeling. I love the walk down to the entry point through a little min-rainforest. The abandoned boat ramp can be very slippery.