Information on bus operators and their authorized rates is maintained in Costa Rica by ARESEP , the public services price regulator.
The following is a list of bus routes, with route number and operator, published by ARESEP. It has authorized prices as of December 14th, 2013, which should be valid for a few months:
You can also download ARESEP's bus fares app on Play Store, this app will give you the current listing of all routes in the country with their fares. The list has two authorized prices. The higher one applies to the general public, the lower one for senior citizens.
ARESEP also has a bus route database, with maps for many routes:
Not all routes have maps on the database currently, but the database should expand in the next few months.
The Costarrican Institute of Tourism (ICT) has an excellent PDF with bus schedules, which is pretty well updated: