PTTravel - offers the ability to query the basic fare buckets on the major airlines. Quick, simple, easy, free. PTTravel is based on a web interface.

SeatCounter - SeatCounter offers a similar interface and details as PTTravel. It is also web-based and free.

ExpertFlyer - offers the ability to query the basic fare buckets and limited reward buckets, review filed fares, review routing rules, display seat maps, plus a few others. ExpertFlyer is based on a web interface.

the KVS Tool - offers the ability to query the basic fare buckets and limited reward buckets, review filed fares, review routing rules, display seat maps, plus a few others. Currently the KVS tool is based on a PC platform (ergo you'll need to have access to a PC to run it) but it does offer limited web support for queries.