I hate when people say/type "xmas"
Actually our pastor said in his seminary they all use "X" to abbreviate Christ, as it's the first letter in the name in Greek, "chi".
So it's not a secular attempt to "x" put Christ, if you will; but rather replacing the name with a shorthand, as seen here an initial.
Just an interesting fact I thought I'd pass along!
Sorry to ambush the thread!! It always bugged me a little too though, 'til I learned that!