WordPress.org currently hosts 6,265 plugins, which makes it kind of hard to figure out which ones are worth using. I have been using WordPress with a long time now and have come across quite a few plugins that I consider to be invaluable. Whenever I install WordPress on a new site, I usually always install the same plugins right off the bat.
Here is a list of 10 plugins (in no particular order) I use on all the websites I create.

Akismet

It comes with WordPress and if you plan on having comments, it is a great spam filter. You must sign up with WordPress.com to get an activation key to use it but it is well worth it.

Google XML Sitemaps

SEO is on everyone’s mind and this plugin helps generate a XML compliant sitemap that is supported by Ask.com, Google, YAHOO and MSN Search.

WordPress.com Stats

There are a few stats plugins out there but I am a fan of using the one developed by the developers of WordPress. This one also requires an activation key from WordPress.com but if you are using Akistmet you already got one.

WordPress Database Backup

I have said it before, and I will say it again, “Backup, backup, backup!” Don’t mess around when it comes to your database. Install this plugin and set up an automated backup just to help you rest easy that all your hard work won’t get lost.

WordPress Super Cache

Load time is very important, and sometimes, all those server requests really bog down a site. This plugin generates HTML files uses them instead of processing PHP scripts every time someone visits your site.

Theme Test Drive

This is a plugin for developers. It allows you to test a theme without making it go live. This is indispensable when creating a custom theme or making a few tweaks.

Add to Any: Share/Bookmark/Email button

Social networking is a great way to help get your site out there, so why not give your visitors the ability to support your site through an easy to use interface. This plugin offers links to all the major social networking sites such as Facebook, Twitter, Digg, MySpace and Delicious.

Highslide Integration

Highslide is an amazing JavaScript thumbnail viewer and this plugin makes it super easy to use it with your WordPress install.

More Fields

One of WordPress’ greatest and most ignored feature is the custom field. It offers the ability to do almost anything with a post and if you have ever used them, this plugin helps make it a little easier by allowing you to create permanent boxes for the custom fields you use most often.

Auto-tags

Tags are great to help organize your posts under similar topics or “buzz” words. And if you are using any of my themes, tags are used as keywords to help with your site’s search engine optimization. It is very easy to create your own tags but any form of automation helps make you work faster and more efficiently.