Clean your WordPress database from post revisions, with Better Delete Revision
Better Delete Revision is a simple and efficient WordPress plugin that deletes revisions of posts from a blog’s database, along with other content related to each revision such as meta information, tags, relationships, etc.
Better Delete Revision will help you keep your database lighter since WordPress tends to store innumerable revisions.
Whenever a post is saved WordPress automatically creates a revision and stores it in the database.
It would be nice if the plugin was able to delete revisions older than x days. Right now you have to use it manually whenever you want to clean your database.