META tags describe the content and keywords that illustrate your blog or web content. It contains important information for search robots to use in adding your blog posts to their search indexes. Several search engines use the information within these tags as part of their algorithms.

You can download a Wordpress plugin that will automatically generate and publish Technorati Tags and HTML Meta Keywords based on the full content of your post.
Once generated, tags can be manually edited to ensure the tags are relevant to the content. Manually editing your tags is recommended because if you have written a post about Ipods and have not mentioned a term, such as “Apple” then it will not appear as a tag, so there’s an audience group that you’re possibly missing.
The plugin is called AutoMeta and it can be downloaded here

The following plugins are highly recommended if you want your blog to be successful. Here is a list of my own top 9 that I use for BloggerHolic.

1. Comment Relish: An excellent plugin that is certainly part of my “must use” folder when setting up new blogs.
2. Social Bookmarks: I use Sociable. It automatically adds links on your posts to popular social bookmarking sites. When ever you or someone bookmarks your posts via the links it will auto fill the URL and title therefore all you have to do is click “submit”
3. Meta Tags: The plugin name is Autometa. It will automatically generate and include HTML Meta Tags and Technorati Tags based on the full text of your post. This is an SEO essential plugin you must install and use. It’s very easy to use; the creation process involves generating a list of all the important words in the article, by stripping out punctuation and then removing common words like the, and, then, a etc. Of course you can edit this and add your own which is what I do every time.
4. Google Adsense: has become the most popular Internet contextual money-making program and integrating Google Adsense into your Wordpress template has become so easy with the many plugins available. The most popular is Adsense Deluxe. It offers advanced options for managing the automatic insertion of Google AdSense to your Wordpress posts. You can easily enable, disable and change your Adsense through the Wordpress control panel.  Click here for a list of the 10 best Adsense related plugins
5. Akismet: Do you get lots of SPAM messages every day in the comments column of your blog? If you do then did you know you can block such spam messages? All you need to do is install Akismet - a anti-spam plugin. It will filter your spam separately so you can delete them from one location within the Wordpress admin panel with a single click. I use Akismet and it works great. Since installing it, it has caught 173 spam comments for me.
6. Send to a Friend: I use WP-EMail that allows people to recommend/send your WordPress blog’s post/page to a friend. A very good plugin that will help to increase the number of visits to your site. 
7. Daily Top 10 Posts: This fantastic plugin tracks the number of pageviews per blog post for TODAY and you can display the results anywhere you want, i.e. sidebar, header, footer, etc. You can see a demo of this on this site just below the header. It tells me and other readers what the most popular posts are for today and how many views those posts get. With the same plugin I can also show the most popular posts overall.
8. Ultimate Tag Warrior: A tagging plugin that you will often see being used on more and more sites. To put it simple it’s basically a list of keywords visible on the sidebar in my case called a “Tag Cloud”. The bigger the font size of that keyword the more popular it is. It’s very easy to use and you can add the tags through the Write post page in Wordpress in a tag box.
9. Sitemap Generator Plugin: I use DDSiteMapGen, an excellent plugin. This plugin creates a sitemap for your site and it’s not just another XML sitemap plugin, but rather a true sitemap generator which can easily be customised from the options page in the Wordpress admin panel. For a demo click here