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.

Liz Strauss Comment Counter is a highly configurable badge (very similar to the Feedburner one, except it’s more configurable) to show off the number of comments your blog has.
This plugin was made in celebration of <a href="http://www.successful-blog.com/" rel="nofollow ugc">Liz Strauss</a> dedication to blog community building so you, too, can show the world how social your blog is.
For a more detailed documentation and screenshots of the interface, please visit its official page: <a href="http://planetozh.com/blog/my-projects/liz-strauss-comment-count-badge-widget-wordpress/" title="Liz Comment Counter by Ozh" rel="nofollow ugc">Liz Comment Counter</a>
Tip: To keep track of this plugin’s evolution and features, you are advised to subscribe to the <a href="http://planetozh.com/exit/feed" rel="nofollow ugc">author’s feed</a>
Ho, and if you like this plugin, please rate it 5 stars! 🙂 ——————–>

Liz Comment Counter by Ozh

A highly configurable badge to show off the number of comments your blog has.

Ozh' Auto Moderate Comments vs Liz Comment Counter by Ozh