The following is my current favorite list, and there’s still tons of other great plugins I don’t have listed here, but if I had to install a new blog, these are the first to go in.

Don’t forget to leave a comment and let me know what your favorites are!

Please note: The versions listed are as of the date of this post. There’s a few that could be redundant, but if you run several blogs, then you can pick and choose different ones to play with.

Add To Facebook
Adds a footer link to add the current post or page to a Facebook Mini-Feed.
Version 1.4.3 | By David Goldstein

Advanced Excerpt
Several improvements over WP’s default excerpt. The size of the excerpt can be limited using character or word count, and HTML markup is not removed.
Version 0.2.2 | By Bas van Doren

Akismet
Akismet checks your comments against the Akismet web service to see if they look like spam or not. You need a WordPress.com API key to use it. You can review the spam it catches under “Comments.” To show off your Akismet stats just put in your template. See also: WP Stats plugin.
Version 2.2.7 | By Matt Mullenweg

All in One SEO Pack
Out-of-the-box SEO for your WordPress blog. Options configuration panel | Upgrade to Pro Version | Donate | Support | Amazon Wishlist
Version 1.6.10 | By Michael Torbert

CommentLuv
Plugin to show a link to the last post from the commenters blog by parsing the feed at their given URL when they leave a comment. Rewards your readers and encourage more comments.
Version 2.7.64 | By Andy Bailey

Dagon Design Sitemap Generator
Generates a fully customizable sitemap
Version 3.15 | By Dagon Design

Exec-PHP
Executes code in your posts, pages and text widgets.
Version 4.9 | By Sören Weber

Facebook Comments TNG
A new and re written Facebook notes comments grabber.
Version 0.18 | By Phil Spencer

Facebook Posted Items
Goes all the way to Facebook and fetches the posted items to show them to you.
Version 0.3 | By Fepe

FeedBurner FeedSmith
Originally authored by Steve Smith, this plugin detects all ways to access your original WordPress feeds and redirects them to your FeedBurner feed so you can track every possible subscriber.
Version 2.3.1 | By FeedBurner

FeedBurner Widget
Adds a sidebar widget to easy customize and display your FeedBurner subscribers stats RSS button.
Version 1.2 | By Alexander Dichev

Feed Statistics
Compiles statistics about who is reading your blog via an RSS feed and what they’re reading.
Version 1.3.2 | By Christopher Finke

Feed Subscriber Stats
This plugin will show the number of subscribers according to FeedBurner.
Version 3.0.6 | By Allan Collins

Flickr Widget
A widget which will display your latest Flickr photos.
Version 0.1 | By Donncha O Caoimh

Gaboinked! Facebook Badge Plugin for WordPress
The Gaboinked! Facebook Badge Plugin for WordPress is a Sidebar Widget that displays a facebook Badge in the Sidebar of your self-hosted WordPress Blog.
Version 1.0.142 | By the Gaboink! network: George Jones

Google Analytics for WordPress
This plugin makes it simple to add Google Analytics with extra search engines and automatic clickout and download tracking to your WordPress blog.
Version 3.2.5 | By Joost de Valk

Google XML Sitemaps
This plugin will generate a special XML sitemap which will help search engines like Google, Yahoo, Bing and Ask.com to better index your blog.
Version 3.2.2 | By Arne Brachhold

Maintenance Mode
Adds a splash page to your blog that lets visitors know your blog is down for maintenance. Logged in administrators get full access to the blog including the front-end. Navigate to Settings ? Maintenance Mode to get started.
Version 4.4 | By Michael Wöhrer

The WordPress Bar
Seen the DiggBar on Digg.com? Add a similar feature to your WordPress blog by creating a navigation bar for all external links outside of blog. Also feature social network links such as Facebook, Twitter, Digg, and FriendFeed.
Version 0.6.2 | By Anthony Montalbano

Twitter for WordPress
Displays your public Twitter messages for all to read. Based on Pownce for WordPress by Cavemonkey50.
Version 1.9.7 | By Ricardo González

Twitter Friends
Displays a list of our twitter followers. Help and tutorials, go to Realhomeincomes.com
Version 1.2 | By Matt

Twitter Widget Pro
A widget that properly handles twitter feeds, including @username, #hashtag, and link parsing. It can even display profile images for the users. Requires PHP5.
Version 2.1.4 | By Aaron D. Campbell

UBD Block Ad Plugin
Let the blog owner add 125×125 block ads to their sidebar. Set your Block Ads here.. Questions on configuration, etc.? Make sure to read the README.
Version 1.1 | By Unique Blog Designs

What Would Seth Godin Do
Displays a custom welcome message to new visitors and another to return visitors.
Version 1.7 | By Richard K Miller

WordPress.com Stats
Tracks views, post/page views, referrers, and clicks. Requires a WordPress.com API key.
Version 1.6.1 | By Andy Skelton

WordPress Admin Bar
Creates an admin bar inspired by the one at WordPress.com. Credits for the look of this plugin go to them.
Version 3.1.7 | By Viper007Bond

WordPress Online Automated Backup
Plugin that allows you to backup and restore your wordpress blog very easily. Read how it works before installing. Requires an account on WordPressBackup.com (free acounts available).
Version 0.8.2 | By LiquidStudios

WP Chameleon
Used for generating random copies of pages or articles for opt-in page optimization or article rewriting.
Version 1.13 | By Gustav Stieger

WordPress Related Posts
Generate a related posts list via tags of WordPress
Version 1.1.1 | By Denis

WP Security Scan
Perform security scan of WordPress installation.
Version 2.7.1.2 | By Michael Torbert

WPtouch iPhone Theme
A plugin which formats your site with a mobile theme for the Apple iPhone / iPod touch, Google Android and other touch-based smartphones.
Version 1.9.7.6 | By Dale Mugford & Duane Storey (BraveNewCode)

Youtube Brackets
Insert YouTube videos in post using bracket method. Enables YouTube blogging to standalone wordpress setups.
Version 1.1 beta | By Robert Buzink