I've been engaging in a personal project recently to get all my OLD wordpress sites upgraded to 2.6 and on the latest versions of plugins and such. This has helped me notice that there are things I'd like to do with the software that it doesn't do by itself, either because of 3rd party services or for SEO reasons.

One thing: I wouldn't create a new WP site without the amazing K2 theme. Just get it. You'll thank me later. No price tag, just CSS and some awesome AJAX, plus plugin integration and an alternate sidebar manager. The theme that kicks WordPress into high gear.

Here are 10 plugins I probably wouldn't deploy wordpress without:

1. FeedBurner FeedSmith - If you use FB, this is a no-brainer
2. Flare Smith - Eric Marden's excellent FeedBurner stats and FeedFlare plugin. No more copy and pasting javascript
3. K2 Hook Up - Every site has those couple of places where you need to paste some javascript for tracking or ads, and K2 provides hooks into all of them. This plugin exposes those to blog admins. Another Xentek creation.
4. Related Posts - I don't think this is in active development anymore. I have no complaints, though. A great reason to have K2 and K2 Hook Up.
5. Landing Sites - Let's get real. Not all visitors hit your site from the home page. When people reach your site via a search engine, this plugin helps you display some helpful pointers to what they might have ACTUALLY been looking for. Useful for very old blog posts. Another great reason for K2 Hook Up.
6. All in One SEO - This is a very recent addition to my list, but something that is sorely needed if you pay attention to your Google Webmaster reports, and you're concerned about how your blog shows up in SERPs (when it shows up in search engines). This plugin is actually pretty brainless, but powerful at the same time.
7. Google XML Sitemap - Again with this one, as soon as I started paying attention to Webmaster Tools, the sitemap stuff was jumping out at me, and I felt the need to address it.
8. Secure Accessible Contact Form - Websites don't exist without contact forms. That's a statement. However, spam and usability can get in the way. This plugin leaves nothing to the imagination, and apparently it's blocked 17 spam on this blog. Go team.
9. FeedWordPress - For planet-style sites or other syndicated sites, this plugin has tons of options but works pretty well out of the box. Integrates with your built-in Blogroll and Categories, too. As I remember, installation is gummy, but this plugin is still an essential part of my toolkit.
10. Akismet - I would have stopped blogging a long time ago if I had to put up with the thousands of spam comments I get on a weekly basis. Wordpress must be an easy target, because the spam rolls in, and it never stops. Ever. Install this plugin no matter what. Requires an API Key from Wordpress.com

This is not an exhaustive list of every plugin I use or endorse, just 10 you should know about, or some that are too essential to pass by.

Honorable mention goes to the built-in WP Widgets - without those babies, life would be hard. K2's sidebar manager actually approaches a new level of sophistication with widgets, and I often wish I were running K2 on this site. Either way, you're getting the chance to display lots of dynamic stuff that lives near the content, without needing to be the content itself.

Lately I'm a Drupal guy, but I still think WordPress has its place in my day-to-day, especially for a blog like this, or when you miss the days of 5-minute setups.

These plugins all (except FeedWordPress) get first priority on every WordPress site I configure for myself, clients or friends. I have donated to several of these developers' tip jars, and I hope that by writing this post, I can do something just as good as loose change in the virtual hat.