I like LUSH solid shampoo pucks and really wish I had discovered them back when I had to travel a fair bit. Instead, I got to try one purely by accident (and sweet, sweet charity) in the middle of a camping trip in northern Sudan - very long story) and was then mildly addicted. They're really nice, but can be a little hard to keep solid and dry before storing (they'll still work if they're kind of melty in the tin, but they're not as aesthetically pleasing that way).
Anyway, pragueloop has come up with a wonderful way of storing the pucks between uses that doesn't necessarily require you to pull the puck out to use it. Very cool. More discussion at pragueloop's blog.