With all of the buttons and toggles I sometimes forget what I have mapped to what. Rather than make and remake a cheat sheet every time I tweaked things I wrote a script to parse the binds and generate it for me, and thought that I'd share it with you.
The website is
http://www.mcdee.net/elite/. You need to select the 'X-55 reference' link on the left-hand side and then upload your Custom.binds file, which you will usually find at c:\Users\[username]\AppData\Local\Frontier Developments\Elite Dangerous\Options\Bindings). Hit 'Generate sheet' and wait a few seconds and it should give you back an image of your joystick and throttle settings.
There is a fair bit of work that needs to be done on it, not least that I haven't yet put in all of the throttle controls, but I thought I'd share this in its current state to see if people find it useful. And, of course, to let me know which of the mappings I've missed!
I'm also not entirely happy with the template images, as I'm currently restricted to the textboxes which are already in place but was too lazy to hunt down and build a new template. If anyone has a nice (preferably layered) template for the joystick and throttle then I'd be very interested to hear from you.
In future it might be possible to expand this to other joysticks, but for now it's X-55 only.
Anyway, if others out there with X-55s can try this out and give me any feedback it would be much appreciated.