Pyfa is a cross-platform desktop fitting application for EVE online that can be used natively on any platform where python and wxwidgets are available.
It provides many advanced features such as graphs and full calculations of any possible combination of modules, fits, etc.
Please see the FAQ for answers to common questions / concerns
pyfa currently only supports wxPython 2.8. However, there are some distros that have started to support 3.0 and subsequently dropped support for 2.8 altogether (such as Debian Jessie). If this is the case and wxPython 3.0 is the only version installed, the official pyfa releases will not run. You must either find a package for 2.8 or compile it yourself.
For Debian Jessie, wxPython 2.8 is available in Sid (the unstable repo). you can use apt-pinning to install select packages from unstable and still keep your stable system. See http://jaqque.sbih.org/kplug/apt-pinning.html for me details.
3.0 support is being worked on and can be found on the wx3 branch. It may be stable enough for you, but there are a few bugs related to it. Please see the wx3 label on the GitHub issues area for me information on known issues (biggest one currently is GTK warning spam): https://github.com/DarkFenX/Pyfa/labels/wx3