An alphametic puzzle (also sometimes known as a cryptarithm) is a type of puzzle where words are put together into an arithmetic formula such that digits can be substituted for the letters to make the formula true. Here are two examples, the first being one of the simplest and the second being probably the best known alphametic puzzle:

    I       S E N D
+ B B     + M O R E
-----     ---------
I L L     M O N E Y

In the first, I = 1, B = 9, and L = 0.

Below are links to my pages dealing with Alphametic puzzles.

Alphametics Pages

Puzzles Lots of alphametic puzzles I've found.
Solver Finds solutions to puzzles.
Fast Alphametic Puzzle Generator Generate your own puzzles.
Slower Generator Same as above but much slower. For use if the above is unreachable.