Must have WordPress Plugins?

All In One SEO Pack
This is an incredibly valuable plugin that's still, shockingly, available at no cost. This plugin automatically creates meta-tags on each post page, allowing you also to pre-establish any meta-titles or meta-tags you want included. All In One SEO is one of the best "plug & play" style plugins available - even if you're new to WordPress and know next to nothing about SEO or WordPress development, all you need to do is install, activate, and write up a storm! There's also a "pro" version available for $39 (for an unlimited license), which is allegedly the "#1 Most Downloaded WP Plugin." They update frequently (sometimes too frequently), but it will definitely do its job in getting your website optimized for search engines.


I-Max Width
Blogging is definitely a writing-based sport, but as most bloggers know, without visual aid, a wordy blog post can make a reader's eyes glaze over with boredom. Particularly for design, fashion, or photography blogs, I-Max width can save you valuable time and frustration by automatically adjusting every image to fit in the content column of any theme. By setting a pixel maximum (i.e. 400px wide), you can ensure that your theme doesn't get distorted, and neither do your images.


ShareThis
In a world of constantly evolving social media, plugins like ShareThis become increasingly important. What sets ShareThis apart from the rest of the social sharing plugins is its compact, flash-based user interface. You can control the number of social media sites to include, as well as the color scheme, text, and general appearance of the plugin. It's by far the easiest way to get your post submitted to important outlets like Twitter, Facebook, StumbleUpon, Digg, etc.


Shortcut Macros
Attention affiliate marketers: if you're tired of looking up the same links over and over, you need this plugin. Shortcut Macros allows you to use short codes such as "##hostmonster" which, after saving a draft or publishing, converts itself into an image, link, php executable... Whatever you designate. This will save you hours and hours of cumulative linking. It can also be used for post headers (using an image tag) which is handy for creating periodical blog columns, differentiating authors, and more. This may be the single most valuable free plugin for affiliate marketers.


TweetMeme
Chances are good you're familiar with TweetMeme even if you don't recognize the name. This plugin has taken the blogosphere by storm over the last few months. adding tiny, light green boxes to the top right of millions of blog posts across the internet. "But if you have the aforementioned ShareThis, why do you need TweetMeme?", you might ask. Well, while ShareThis includes a comprehensive list of all mediums of social media, TweetMeme is an eye-catching, one-click way for users to share your post, and it also offers link tracking capabilities, so you can see exactly who, where and when your link was posted on Twitter. One important reminder: Remember to configure this plugin as soon as you install it, otherwise all of your retweets will define the source as "@tweetmeme" instead of your personal twitter handle.


WP-Stats
The classic statistics plugin makes yet another "must-have" list. While WP-Stats may not be the most technologically advanced, beautiful, or complex plugin available for statistics tracking, it's definitely the most user-friendly. They have been making some excellent upgrades over the last few months, including the ability to see how many hits you get on your home page, instead of just specific posts. While Google Analytics or Quantcast may deliver more in-depth, detailed reports - when it comes to statistics available in your WP dashboard, WP-Stats is still tops.


Theme Tester
While you may not be using this plugin more than once or twice per year, it's extremely important when the time comes to modify your site's design. I used to put up a "Maintenance Mode" splash page on my blogs when changing the design, but that lost valuable hits and even more valuable affiliate link clicks (which means lost money, and that's never good). Theme Tester allows you to install new themes and activate them, visible only to the administrators of the blog. Your readers still see the previous design while you customize images, CSS and HTML on your new theme. Then, just activate the theme as usual and all your customizations will be saved, and your new design goes live without worry.


WP-Polls
Getting feedback from your readers is probably the most valuable information you can collect from your blog. If you know what they like, you know what to give them. WP-Polls allows for AJAX-enabled poll insertion into sidebars, pages or individual posts. You can cap the number of responses (I like to cap it at 100 for demographic-related polls, for each percentage-creation used in media kits), as well as filter the responses by guests, registered users, and/or comment authors.

CommentLuv
It's come to my attention that the majority of comments on blogs are from... well, other bloggers. Often times, they are quick, basic, and spammy - just looking for another place to put their link; but other times, these comments are insightful and delivered by peers who actually deserve a link back, as your readers will likely benefit from their knowledge. CommentLuv offers an easy way to give those readers a little something extra for commenting on your blog (encouraging comments is always a good idea) by pulling their most recent blog post from their RSS feed, and displaying it right below their comment.


Exec-PHP
This is exactly what it looks like: a plugin that allows you to execute PHP/javascripts from within individual posts, sidebar widgets or pages. Sweet, simple, and extremely effective. Use it to display feeds, news reels, or anything else you can dream up.


From 10 Must-Have Free WordPress Plugins | Best WordPress Plugins

I have found the following plug-ins must have for any Wordpress blog:

All in One SEO;

Akismet;

Related posts;

Max Banner Ads (especially if you want to promote affiliate programs).

while i totally agree that this belongs in the all-in-one thread... i'll bite (why not)


these are a must :

max blog press ping optimizer
fixes WP pinging system
all in one seo
needs no explination
google sitemap
generate xml sitemap
Dagon Design Sitemap Generator
generate html sitemap
seo slugs
takes words like if, and, or, the out of permalink because the SE's ignore
wp-db-backup
because you can never be too safe
either dean's fck editor or tinycme advance
because tinyMCE sucks just see for your self
exec php
lets you execute php in posts, pages, and text widets


these i commonly use, but depends on the site if it's useful or not :

exclue pages
lets you chose to exclude pages from navigation menues
rss include pages
include pages in rss feeds
wp-related posts
lets you insert related post links at the end of posts/pages
rss footer
includes an extra title/link/description at the bottom of each article in rss feed
fuzzy seo
looks like tag cloud but populates with search terms that poeple used to find you from SEs
what would seth godin do
uses cookies to manage determine if a user has visted before or not, then you can adjust wha they see accordingly. ie, "i see your a first time visitor, please...."
subscribe me
nifty little RSS subsribe button that when you hover gives the option of many social media networks to chose from


WP Super Cache - good if I expect people to actually browse my site, but i dont use on landing page sites or sites where i dont expect them to leave the front page


Temporary :
Theme Tester
Theme Tweaker

i install both of these until i pick a theme and a look, then i unintall the themes i didnt use and manually tweak the theme files to use the colors i chose then unintall plugins when i am done


im sure there are others i use from time to time, but i'd say these are my favorite

and it just looks so cool!!

SEO Smart Links is my new fav because it is great for linking to other posts or affiliate products, it's just a bit labor intensive because you do it manually.

no one mentioned wp auto tagger - automatically detects and adds tags to your posts.

Do a search for Adsense Injection. It is a plugin that puts whatever size adsense blog on every page. I decided to try this on a site with good traffic and just a one adsense block on the siebar and the site went from $200/month to $1000 per month. Nice return for just one free plugin.

Actually I see that for three days his site is down. If you want to grab adsense injection I downloaded and served it up on my site for convenience sake. Just go to this link:

Adsense Injection

Hope you guys like this as much as me.

WP-Stats-Dashboard

wordpress.org/extend/plugins/wp-stats-dashboard/

Thanks for the shout outs, Sheila... how often are you republishing your posts?

Here's one I haven't seen mentioned

--> Google Optimizer Plug-in -- allows you to run split tests in a WP blog through Google Web Optimizer.

Try

WP-supercache
Increases the speed it takes for your website to load for visitors comming back.