Soap in Bed
Yes, really. Many people claim to prevent leg cramps by keeping a bar of soap between their bedsheets.
Snopes.com, the “go to” website to determine the validity (and usually falsity) of urban myths, gives soap for leg cramps an “Undetermined” label. The site states that while no one knows why this remedy might work, there are a lot of anecdotal claims that it does work.
Interestingly, the size of the soap doesn't seem to matter (small bars of soap in hotels supposedly work fine), or even if the soap is wrapped or unwrapped. All soap seems to work, although there have been some reports that Dial and Dove soaps are not effective.
Again, none of this involves any scientific research. It's all anecdotal. But if you're trying to avoid leg cramps, what's to lose?