Updating entry WITHOUT updating timestamp

Don't use timestamps, but track times manually.

If you really want to update a record and don't update it's timestamp, use:

UPDATE `table` SET `timestamp` = `timestamp`, `col` = 'new data' …;

Is there a way to manually disable updating the timestamp on a special occasion? (eg: updating the entry to revise a blog post, but not to re-date it)

Sounds like you need to configure the default constraint so that it populates the column on insertion only:

DEFAULT CURRENT_TIMESTAMP

Changing it to only be this means that any revisions will not trigger the timestamp value to be updated. IE: If you created the blogpost yesterday, and corrected a typo today - the date in the column would still be for yesterday.

To make your table/timestamp auto-update:

ALTER TABLE myTable
CHANGE myTimestampColumn
        myTimestampColumn TIMESTAMP NOT NULL
                       DEFAULT CURRENT_TIMESTAMP 
                       ON UPDATE CURRENT_TIMESTAMP;

To make it not auto-update:

ALTER TABLE myTable
CHANGE myTimestampColumn
        myTimestampColumn TIMESTAMP NOT NULL
                       DEFAULT CURRENT_TIMESTAMP;

NOTE: The "default current_timestamp" part just sets it to the current stamp at default time, since the field is not-null. You can remove both the not null and the default, if you like.

You can manually set the value of the column to its current value in the update command:

UPDATE table SET x=y, timestampColumn=timestampColumn WHERE a=b;

If you don't set the value in the query, it will be updated to the current timestamp as per the table definition.