Guam and Saipan (if you can find a reason to get there). 84 degrees at 130 fsw; 150 viz; no crowds; and cheap rental places.
Hawaii is a close second. Use the MWR at Schofield, as they have the cheapest dive rental prices I have ever seen, and it's all brand new top of the line gear.
Guam and Saipan, definately some of the best space A...and the BEQ...smooth
I have to agree, Saipan has some of the best diving there is. I was stationed in Okinawa for a couple years, and loved the waters there, but the diving in Saipan is just amazing. As far as a specific dive site, the Grotto was my favorite. If you want to see some sea turtles, though, I would suggest Lau Lau Bay. Also, if you are looking for a down-to-earth dive guide/instructor that knows all of Saipan's dive sites like the back of his hand, AND gives a decent military discount, I highly recommend getting in touch with Harry at www(dot)axemurderertours(dot)com. He seriously knows his stuff. You won't get the typical dive tour with him, and he will probably even show you a bit of the island.
Happy Diving!
P.S. - Sorry about the URL link...apparently you have to post 5 or more entries before being allowed to post a link...