W-Shadow.com

Admin Drop Down Menu
An indispensible plugin that makes navigating the admin panel much easier. The only problem is that I tend to accidentaly move the cursor outside the “hover” zone, resetting the menu, meaning I have to start over.

Broken Link Checker
Checks your posts for non-working links and lets you know (on the dashboard) if any are found. It’s of the “set and forget” kind, as it does the checks in background. Sometimes generates “false alerts”, probably because no site is up 100% of the time. And yes, this is one of my creations 😉

Exec-PHP
The best plugin for executing custom PHP code in your posts and pages. I’ve used it to turn a blog into an e-commerce website (well, I was too lazy to design a site from scratch, so I just added payment validation and download handling routines inside WP pages).

Preview Frame
Brings back the handy preview frame to the edit page. As simple as that.

WordPress Automatic Upgrade
Does exactly what it says on the box. This plugin automates the whole updating process, which is very handy. Everyone should be using it. No, really! I wouldn’t be surprised if this plugin was integrated in a future WP release.

WP-Syntax
A very nice syntax highlighter for all the programming-related blogs (and some other, too). Supports lots of different languages. You can see it in action by browsing through the “Programming” category of this site.

Conclusion
I bet there really is at least one plugin you hadn’t heard about in the above list 🙂 I tried to find some plugins that aren’t on everyone’s “Must Have” lists yet, but are still useful.