This article in the MySql manual explains all the string functions.
Provided that the format of the field is consistent throughout the records you can use the following:
SELECT
CONCAT(SUBSTRING_INDEX( 'Joe M. Blow', ' ', -1),
", ",
LEFT(SUBSTRING_INDEX( 'Joe M. Blow', ' ', 2 ), CHAR_LENGTH(SUBSTRING_INDEX('Joe M. Blow', ' ', 2)) -1))
FROM
table name etc....
(Replace Joe M. Blow with the field you need. I presumed that you want the final "." after the initial is not needed. If you do need it you will have to use this:
CONCAT(SUBSTRING_INDEX( 'Joe M. Blow', ' ', -1),
", ",
SUBSTRING_INDEX('Joe M. Blow', ' ', 2))
FROM
table name etc....
