Wordpress has a nice little revisions feature that will allow you to revert to a previous version of a post if you don't like the current edit. However, the drawback of this feature is that it is not always needed and it fills the post table full of stuff you will never need. Fortunately, turning this feature off isn't too much of a pain. All you need to do is add the following line of code to your wp-config file, just below the DB_COLLATE line.
You can also set the autosave interval here to something greater than the default of 60 seconds. It is possible to do this in the wp-config file since version 2.5.0.
If you want to get rid off all of the post revisions from your post table then you can use the following SQL query.
DELETE FROM wp_posts WHERE post_type = 'revision';