Hi, I am living on Majuro, halfway in on a 2-year contract, and will be here in March 2011. Majuro is accessible, but the only commercial carrier is Continental (either through Hawaii, or Guam).
There are a couple of hotels here which are quite decent. I usually tell new arrivals that 95% of the beauty of the Marshall Islands is underwater, and it is tru of Majuro.
The only remaining dive operator on Majuro is Japanese, catering almost exclusively to Japanese charter operations, but there are lots of divers and a couple of instructors on island always willing to assist in arranging tanks and boats. Currently Majuro can only provide air fills (no EAN or tri-mix), and you can borrow tanks. A tank fill is about $5. Gear is difficult to get here, so bring your own. There is also a functioning decompression chamber on island now!
Both lagoon and ocean diving is amazing and accessible from shore. The lagoon has a number of pinnacles worth visiting by boat, a few WWII and modern wrecks, and the Calalin channel is a popular destination. Since we are an atoll, the reef drop-off is steep, dropping to 6,000 feet and beyond within 1,000 feet of shore.