Adam: there's randomize-lines:

Package: randomize-lines
Maintainer: Arthur de Jong 
Description: randomize lines of input text
 rl is a command-line tool that reads lines from an input file or stdin,
 randomizes the lines and outputs a specified number of lines. It does this
 with only a single pass over the input while trying to use as little memory
 as possible.
 Currently randomize-lines is under development and command-line arguments
 may change slightly until a 1.0 release is made.