I have tested some plugins and found that these are the easiest to use.  Furthermore, I will only mention the plugins that I use with WordPress version 2.6.3.

Contact Form 7 – When you click on the email tab, you will see a form.  This form once filled and submitted will go straight to my email.

Duplicate Post Checker – Checks for duplicate posts already posted.

Homepage excerpts – Instead of seeing the whole article, you can truncate older articles.  I chose to truncate all articles except the first four.

WordPress.com Stats – Allows me to see basic information such as search terms used to find my site, popular articles, etc.

WP-reCaptcha – Ensure that comment is submitted by an actual human.

Akismet – Catch spam comments from being posted.

TAC (Theme Authenticity Checker) – Checks themes for malicious code

WordPress Exploit Scanner – Checks database and other files for malicious code.

WordPress Revision Control – Keeps in check the number of revisions kept.  Without this, you could end up with 100 or more revisions in the database for one post.

A huge list of compatible plugins is listed in
http://codex.wordpress.org/Plugins/Plugin_Compatibility.
Choose the version that you are using.  For this blog, I would chose 2.6.