I've always been a bit annoyed by not being able to convert data from my Raymarine C-Series chartplotter into an open and accessible format, such as GPX. Although there are some tools available that support the FSH files written by these chartplotters, they are either not-free or very limited - such as not supporting all data (such as tracks), or by only running on Windows.
I want to be able to back up the data (waypoints, routes, and tracks) on my chartplotter and load it into OpenCPN, so I started to write a python script to do so, available on github. In it's current form it's very rough but exports waypoints and routes to GPX which I can then import into OpenCPN.
The script doesn't yet support tracks, nor is it very resilient or stable in decoding values, but it's a start. Since no other freely available, cross-platform solution exists for converting FSH files, this is a free, open-source project licensed under the GPL.
Long term, once the FSH format is fully decoded, the plan is to turn this into a GPS Babel module. Until then, give this Python script a try.