Tobacco Caye Lodge and Reef's End both have phones & emails so you can book ahead if you feel like it... for anything else, show up and see what's available. Checkout time is 10am.
Tobacco Caye Lodge
The best value and probably most popular place has several bungalows looking out towards the sea, under some hammock-strung palm trees. The food here is pretty tasty as well.
Reef's End Lodge
The most expensive place is nice, but questionably worth the $$.
Gaviotas
A decent cheap option, run by Belizeans.
Tobacco Caye Paradise
A cheap place with good food and a few very rustic cabins built right over the water.
Lana's on the Reef
Small rooms, good food.
Fairweather Place
A small two-story place, with a room or two on the upper floor, above the owners house. It's not entirely appealing, but it's mentionable since they'll let you pitch a tent out front if you prefer to camp. Make 'em an offer.