Posts Limit will limit the number of posts your members can add in a specific time range. You can set the limit by usergroup. After the limit is reached your members will not be able to add more posts until the limits are reset. You can reset the limits manually, or you can setup a cronjob making the limits being reset, for example, every day at midnight. With this app you can control SPAM by limiting the number of posts your members can add each day or hour and so making them realize that quality is better than quantity.
(Link on the right block)