Permutations[list] generates a list of all possible permutations of the elements in list.
Example: Permutations[a,b,c] .
There are permutations of a list of distinct elements.
Repeated elements are treated as identical.
The object list need not have head List.
See The Mathematica Book: Section 1.8.15.
See also: Sort, Signature, Reverse, RotateLeft.
Related packages: DiscreteMath`Permutations`, DiscreteMath`Combinatorica`.