I know what you are thinking, but this isn't just another WordPress plugin blog post. I am asked every few weeks what WordPress plugins I would recommend, and I always end up giving a disjointed list of some from the top of my head. So instead of doing this I thought it would be a good idea to write down the plugins I use quite a bit and would recommend other to use. I will also try to add any alternatives (if they exist) to plugins I use.
Although WordPress is pretty good in terms of SEO it could still use a little bit of help, this is where the All In One SEO Pack comes in. It allows the creation of description and keyword tags for each post, as well as a whole raft of other features, most of which I never need to touch.
Whilst researching this post I found out about a neat alternative called WordPress SEO, which appears to be a viable alternative.
XML sitemaps are important from a SEO perspective and this plugin is the best solution for creating an XML sitemap for your WordPress site. As well as creating the sitemap it can also be made to ping this to a couple of different search engines, which helps your new pages get indexed quicker. The great thing about this plugin is that once you have installed it you can just get on with running your site without having to reconfigure your sitemap every time you post. You can also visit the Google XML Sitemaps generator homepage for more informaiton.
There are lots and lots of contact forms available for WordPress but I tend to use cformsII for my personal sites. cformsII is very feature rich and will let you construct one of more contact forms containing one of several different components available. cformsII was originally part of the WordPress plugin directoty at one point, but was removed when Delicious Days started to charge for it. This plugin is now free but is not part of the directory yet so as a result all updates must be manually uploaded over FTP, which is a real pain. It is possible to modify this plugin to create your own form components and actions, but I have never had much success doing this.
Before using cformsII I used to use Contact Form 7, but for some reason I made a switch over to cformsII. This was a couple of years ago so the chances are that Contact Form 7 is a littler better than it was back then.
There are lots of alternatives to contact forms, but if you want a really solid contact form solution then you should consider Gravity forms. You have to pay for it, but you can get a development licence that will allow you to put it on as many sites as you like. You might be thinking "why pay for a plugin?" but until you use Gravity Forms you have no idea how good it is. You also pay for support so if you are trying to modify it or having trouble installing it onto a site you can just send them a message and they will help you out.
Once your WordPress site is complete you should definitely install a caching plugin so that you will be ready if it gets popular. This kind plugin of deserves its own post really. There are plenty of caching plugins available out there, but the one I have had a lot of success with recently is W3 Total Cache. W3 Total Cache has a whole raft of options and functions, including the ability to cache your content to a CDN.
I have used WP Super Cache and Hyper Cache in the past so if W3 Total Cache doesn't seem to work on your site and server setup then you can always try one of these other ones.
Managing the page hierachy in WordPress can be a bit of a hassle. Going into each page and setting the page parent of each is a real pain, which is where this plugin helps out. It basically creates a drag and drop list of pages that allows you to move pages around the page hierachy with ease. The small number of interface bugs it has is vastly preferble to moving pages around manually.
My Page Order is also available and seems to do the same thing as Pagemash.
Creating a mobile theme can be a lengthy and time consuming process, but this plugin solves all of that by generating a nice looking theme for mobile devices. This plugin will work with iPhone, iPod touch, Android, Opera Mini, Palm Pre, Samsung touch and BlackBerry Storm/Torch mobile devices.
If you are on a shared host then you will most likely be without a backup solution, in which case WP-DB-Backup is a massive must. This plugin will make regular backups of your site and email them to a specified email address.
This plugin adds some little (but essential) tweaks to your WordPress install. Theses are things like removing core and plugin update and WordPress version information for non-admins.
This plugin actualy comes as part of the WordPress download and is a very handy spam filter. You need an API to run the plugin but getting one is nice and easy and will keep your comments mostly spam free.
Until I went to WordCampUK 2010 I would never have thought that using WordPress as a e-commerce platform was a viable solution. After meeting one of the developers of the module I was pleasantly surprised. The WP-Ecommerce module looks very polished and is in production use on lots of sites. Have a look at the WP e-Commerce home page for more information.
Keep an eye out for the next major release, which will feature custom post types for products.
If you use a WordPress plugin a lot and I haven't mentioned it, or you know of a good alternative to one of the plugins I have described here then post a comment and let me know.