Really simple code I thought up a little while back
a is 000
b is 001
c is 002
d is 010
etc.
You go through the whole alphabet and then you get to 222, which will signify that the following string of three will be read as punctuation/numerals
Really easy to crack, of course, but then you can perform some numeric operations on it to make it more complicated to translate, but it's easily translated by a machine.