Wordpress plugins greatly expand the capabilities of your blog! I will list all the plugins that are of special interest for seo, marketing, securuty, and expanded fuctionability.

Adsense-Deluxe - Place Google AdSense ads in your WordPress Posts. Requires WordPress 1.5 or higer. For complete usage and configuration click on AdsenseDeluxe under the “Options” menu. This plugin is very configurable, and you can store different adsense layouts. This gives you the ability to add adsense right in your posts for greater relevant ads!

Subscribe me - Displays a tile with subscribe buttons. To use, call sem_subscribe_me(); where you want the tile to appear. Alternatively, do nothing and the tile will display when wp_meta(); is called. Admin interface is courtesy of Duke Thor.

Auto Links - Automatically turns keywords to popular websites into links. Powerful plugin useful to store all your affiliate links, and regular sites you would link to. By assigning keywords for each links there is no need to type in the links, auto links automatically creates the links for you. Can you see the possibilities?!

Customizable Post Listings - Display Recent Posts, Recently Commented Posts, Recently Modified Posts, Random Posts, and other post listings using the post information of your choosing in an easily customizable manner. You can narrow post searches by specifying categories and/or authors, among other things. Useful for optimizing your blog for ses and adsense!

Smart Update Pinger - Replaces the built-in ping/notify functionality. Pings only when publishing new posts, not when editing.

Bot Check - Checks for human input on comment submission. Requires minor modification of wp-comments.php (see install.txt). An image is generated with a number, if this code is entered correctly in the form, the comment will be posted. If not, it won’t.

Follow URL - This plugin strips nofollow tags from your comments and comment author URL, which are inserted by default in WordPress 1.5

No Duplicate Comments - Prevent visitors from leaving duplicate comments/pingbacks/trackbacks to a post.

Trackback Validator - Eliminates spam trackbacks with surprising accuracy (see website for details).

StatTraq - This plugin will allow you to keep track of every hit on your public WordPress site (note that it does not track admin activity). Very good stats plugin!

WordPress Database Backup - On-demand backup of your WordPress database. MUST HAVE! (also see http://www.tamba2.org.uk/wordpress/restore/ for instructions on how to restore!)

Alismet - Say goodbye to comment spam, you never even have to look at it again!

Gravatars - adds a personal and social touch to your blog!