When a post gets old, instead of simply closing the discussion, send comments and trackbacks to the moderation queue. This will greatly reduce spam.
For documentation and tips, please refer to the official plugin page for <a href="http://planetozh.com/blog/archives/2005/02/02/wordpress-plugin-auto-moderate-comments/" title="Auto Moderate Comments" rel="nofollow ugc">Auto Moderate Comments</a>

Ozh' Auto Moderate Comments

When a post gets old, instead of simply closing the discussion, send comments and trackbacks to the moderation queue.

You have a blog. You have stats telling you how many people read it. You post links. But do you have something telling you how many people click on your links? Count clicks on your files (download counter) or on any links.
For documentation and tips, please refer to the official plugin page for <a href="http://planetozh.com/blog/archives/2004/09/17/click-counter-plugin-for-wordpress/" title="Click Counter" rel="nofollow ugc">Click Counter</a>

Ozh' Click Counter

You have a blog. You have stats telling you how many people read it. You post links. But do you have something telling you how many people click on yo …

Ozh' Auto Moderate Comments vs Ozh' Click Counter