Some of the cheaper accommodations that have websites are:

Secrets Cabins (on the beach) http://www.jamaicalink.com/secrets/index-2.html
Jah B’s (on morass side of beach) http://www.negril.com/jahbs/rooms.htm
Roots Bamboo (on the beach) http://rootsbamboobeach.com
Eddies Tigress (west end) http://www.realnegril.com/tigress2/index.htm
Negril Yoga Centre (on morass side of beach) http://negrilyoga.com
Primrose Inn (west end) http://www.negril.com/hotels/primrose.htm
GreenLeaf Cabins (on morass side of beach) http://greenleafcabins.com
Bourbon Beach (on beach, live music) http://www.bbnegril.com/
Alfreds (on beach, live music: http://alfreds.com/rooms.html


There are many more possibilities including places that do not have websites. If you plan on staying for several months, suggest you rent a place for a few days and then have a look around to see what is available.