Limit Login Attempts
http://wordpress.org/extend/plugins/limit-login-attempts/installation/
WordPress Security Threats That You Should Look Out For
http://wp.tutsplus.com/tutorials/security/wordpress-security-threats-that-you-should-look-out-for/
Timely All In One Calendar
Duplicate Post
Duplicate Post Plugin
How To Clean Up & Optimize Your WordPress Install
http://line25.com/articles/how-to-clean-up-optimize-your-wordpress-install
A Web Designer’s SEO Checklist (Including Portable Formats)
http://webdesign.tutsplus.com/articles/general/seo-checklist/
BackUpWordPress
BackUpWordPress will back up your entire site including your database and all your files on a schedule that suits you.
Tiny MCE Advanced OR Ultimate TinyMCE
plugin for more options in editing
Enable Twitter to Facebook
Use twitter account to do this.
“Add Link to Facebook” Plugin
Allows you to post your blog posts to Facebook automatically. During setup, create an app, activate it using your own account, and then you will be able to choose the page that you want it update after that within the tabs.