Trimming is an important part of control design. By finding natural equilibrium points in a system, less control effort is required to keep the plane flying as desired. This software lets you compute trim points for aircraft ranging from the easystar and quadrotors to f16's and 737's. Anything that can be modelled with a JSBSim model will work.
There are many JSBSim models already developed for flight simulators like FlightGear that can be used as low fidelity models. For higher fidelity models, wind tunnel data can be used within the JSBSim file as done with the easystar model in mavsim. All of this software is open source and available for download.