I have a dual-boot PC, one has windows and one has Linux. They both have minecraft, and I've like them to share the same savegame/server data.
Is this possible, and if so how do I set it up?
You can use pendrive to hold savedata, you can use Dropbox, or make a symlink to the windows partition on Linux.
I know a method with the new launcher which works both ways.
Just a little note: If you use the grub bootloader and you leave windows hibernating, then boot linux you cannot play your saves. I don't know why you would do that, but i just happened to forget windows was on and boot Ubuntu this morning. I had trouble making the windows path from earlier because Ubuntu refused to see the windows partition.