This is the short list of Wordpress plugins I have found useful, and point people towards when they are setting up a self-hosted Wordpress blog.

• Spam Karma - eats spam like it's noones business
• Wordpress Mobile - puts a mobile friendly front-end on your blog
• Notable - so readers can submit your entry to their favourites SNS
• Print - formats your blog posts in the perfect format to kill some trees (turns URLs into footnotes, etc)
• CAPTCHA - the 'are you human?' test to stop spam-bots.
• Google XML Sitemaps - generates an XML file that let's your blog be indexed properly by Google etc.
• AJAX Edit Comments - "allows users and admins to edit comments on a post. Users can edit their own comments for a limited time, while admins can edit all comments."  Neat!

Advanced:

Post By Email - Which I use to fire off quick posts from my smartphone via email.  Once it's working, it's damn handy.  But it's a little tricky to get running.

     Things to note (that aren't noted in the plugin doco):

• If you're sending these from an email address that is different to the one set up for your current (ie Admin) account, you must create a new account, with Author role set, and with that email address.  (Otherwise, the posts get set to Pending Review).
• If you don't have access to cron jobs, or know WTF that means, then follow these instructions.