Here are a few plugins that I think deserve more attention. These will probably be more useful to power-users who really want to tweak their WordPress site, but I encourage everyone to get their hands dirty every once and a while and get creative with their installs. Unless otherwise noted, these should work with with both WordPress 2.92 and WordPress 3.0.
This gives every widget an extra field in which you can specify WP’s conditional tags. What this means is that you can have certain widgets appear on certain pages but not others. For example, I have my blogroll set to only appear on my front page.
This plugin can automatically add alt text to any image that doesn’t have one already. You can use the post title or the name of the image. This is great if you have a blog with lots of images that were never properly tagged and you don’t have time to go through and change them all by hand. It can also override WordPress’s default alt text – this would be useful if you have a group blog where one or more contributors frequently neglects to put any sort of alt text into their images.
I’ve only recently discovered this plugin, and I’m totally in love with it. It lets you sticky or order posts within a tag or category. I’m experimenting with using this plugin to sticky “portal” or “best of” posts to the top of certain tag archives.
This is an amazing plugin that lets you have different domains, titles, and taglines for the same WordPress install. If for some reason you don’t want to use redirects, you can use this plugin to host mirror sites from the same install. You can see it in action on the plugin authors pages lightpainting.org and mcaleavy.org.
Platinum SEO Pack and All-in-One SEO Pack usually get all the attention, but Headspace2 is worth some special attention. It gives you far more (possibly too much) control over your WordPress site’s title and meta-description tags. Some users will find it overkill. I like it because it lets me set descriptions for category and tag pages. Note: This doesn’t seem to work with WordPress 3.0 yet.
All security plugins
I also think pretty much all WordPress security plugins are underrated, which is why I’ve been covering that subject.
What plugins do YOU think are underrated?