While there are many WordPress plug-ins that I use I have to say the three that I cannot do without are All-in-one-SEO, Tweetmeme and wp-db-backup.
All-in-one-seo is very important because it gives you the flexibility to assign seo optimized attributes to your blog and also to your individual blog posts. With the plug-in you can customize how the title tag looks as well as adding some important seo characteristics to the blog post. You can add keywords and descriptions to each blog post to optimize it for seo ranking. You can also set defaults for your entire blog as well as
The next one I consider a must have is tweetmeme. This allows you to have a button at the top of each post that makes it easy for people to retweet your blog post. This has several advantages. It shows social proof about your blog post and can also help drive some additional traffic to your blog because you are getting exposure to your followers followers.
The last one I consider a must have is wp-db-backup. This allows you to backup your database on a regular basis and have the backup emailed to you or saved on you web server. I recommend having it emailed to you. This is important because if you only save it on the server and your server goes down you lose your only source of restoring your WordPress blog. WP-db-backup also allows you to select the schedule and the tables you want backed up and when.
