Accommodation
The listings below are my favorite places.
If you are coming for a short stay, there are places to meet any budget. Not many of the cheap places accept advance bookings, but since there is such a choice this isn't a problem. Show up, drop your bags off at Coconut Tree Divers and go find a deal!
If you are staying 4 weeks or more you may want to rent an apartment, they vary from $200/month upwards. Some of the IDC centers will have a few apartments they offer to Pro candidates. Make sure it has a kitchen so you can keep your eating costs reasonable.

Budget less than $30/night
Coconut Tree Divers - The best value in town has to be the $5/night air conditioned dorm room at Coconut Tree. Only for people diving with Coconut Tree.
Casa Del Sol. This hotel located at the entrance to West End is great value! Beautiful rooms, great prices, very central location. Doesn't have a view, but the great value on everything else more than makes up for it.
Chillies - Rooms and cabins with shared bathroom, $30 single/double rooms main house, $25 single/double rooms in cabins. The water is cold in the cheaper rooms, which after a day diving isn't always a great prospect!
Mariposa Lodge - Has a variety of rooms in a couple of buildings. I understand you can get a bed for the night for as little as $20.
Valerie's - I HATE this place. Rooms are regularly robbed. You will be kept up all night by roosters who start crowing before you go to bed! The rooms are damp and smelly, the bathrooms are dirty and the water is cold. It is cheap, but not cheap enough.
Dolphin resort has two fantastic rooms for four people which cost $35/night. They have one of the best views in town!
Milka's Place - Starting at $10/night for a double room, behind Pura Vida, next to Mariposa. Its reasonable budget accommodation.
Rudi's is even further down the strip past Pura Vida towards Fosters Bar and Grill. I have had a few good reports, a room goes from about $10.
MID Range $30-$90/night
Posada Arco Iris is very nice. It is central and clean and great value if you need those extra creature comforts such as private bathroom. It does have captive monkeys though which I don't like. ROOMS - bathroom/hot water, ceiling fan and refrigerator. High Season US$35.00 - low season US$28 Air-conditioning (optional US$10.00). ONE BEDROOM APARTMENT - One bedroom with full-size bed, one bathroom with hot water, fully equipped kitchen, dining room, ceiling fan and large deck. Ocean and garden view, 2 persons high season US$50.00 low season US$40.00 additional person US$5.00 (max4) Air-conditioning (optional US$10.00). TWO BEDROOM APARTMENT - two bedrooms with full-size bed, one bathroom with hot/water, full-equipped kitchen, ocean views, dining room with full-size bed, ceiling fan and large deck. 4 persons high season US$65.00 - low season US$55.00 Each additional person US$ 5.00 (max7).
Posada Las Orquideas - Sister hotel to Arco Iris, quieter location, on the water with refreshing sea breezes.
Mame Tree Bungalows, near Coconut Tree these bungalows are well equipped, well placed and ,well lets just say the decor is interesting!
Coconut Tree Cabins- Has a few nice cabins very centrally located. The prices go from a single room for $35 , double for $50, two bedroom cabana $90, three bedroom cabana $130.
Half Moon Bay Cabins. - located in a quiet corner of half moon bay. I don't know much about them, they seem nice, I think they attract more middle aged customers. Prices vary from $38 for a single with fan to $95 for a four bed place with A/C.
UPSCALE $90/night an up
Cocolobo - This place in VERY nice and my top pick of any place to stay. Amazing water front views, quiet location, extremely friendly with a lovely pool and deck on the water for sunset drinks
Beach House with their nicest sweet costing $200/night and there other suites costing $150/night.
Outside West End there are loads of nice resorts dotted all over the island. I like West Bay because it is still convenient to enjoy the restaurants and bars of West End. West Bay has many nice places to stay my preferred option is:
Bananarama - Terrible name, but good dive resort, the dive op is run by Mal (British) and Sofia (Argentinean), these two are very experienced and run a tight ship!
Mayokolodge. At about $20,000 a week this place is expensive, but worth it. It has six double cabins your own chef, driver, maid wine cellar etc etc etc. When divided between 6 couples the cost is actually quite reasonable, and well worth a look.