As flight simulation enthusiast you are usually all in one, which means you are your own dispatcher, ground crew, captain and first flight officer. As in real live also for a simulator flight careful flight preparation is essential. Flight preparation starts with route planning, checking the observed and predicted weather, and the performance and fuel calculation. There are quite a lot of tools available with the intention to support you in one or the other way. Some try to support all aspects, others are specialized for route planning or performance calculations only. Some of them are payware, others are free or available for a small donation respectively. I do not pay so much attention whether a tool is for free or not, the important thing is that the tool enhances the process of flight preparation with the focus on professionalism and time saving.
IFR Route Planning
For route planning I personally prefer FP2FMC and FlightplanPro. FP2FMC uses the route generator of rfinder, a well-known web based route planning tool. FP2FMC has the option to save the flight plan in booth FS9 and IVAO compatible format.
FP2FMC generated flight route from EGSS to EDDS
FP2FMC needs the PMDG AIRAC-CYCLES from Navigraph for the final route calculation. You don't need to have installed PMDG for that, only the nav data has to be available in the required structure than PMDG would be installed.
Preview of an IVAO flight plan as stored in the IVAO flight plan directory
I have installed the flight plan tools on my home office PC, so I can make the flight planning Independent of the flight simulator power-up status. The created flight plans are stored on a network storage devices and with start-up of the flight simulator the flight plans are automatically deployed to the IvAp and to the FS9 flight plan directories. The deploying process is performed by a small script which is executed during the FS9 startup phase.
During preflight preparation I load the FS9 compatible flight plan into the PM CDU (pressing twice the RTE button on the CDU) and the IVAO flight plan into IvAp.