RSS2twitter
Cool web app that taps into the Twitter API. Basically, you give it a feed URL and it will post updates to that RSS feed into your Twitter account.
(tags: twitter twittertools rss)

16 Useful .htaccess Tricks and Hacks For Web Developers
.htaccess files make Apache so much easier to work with. Here is a decent list to get you started.
(tags: webdev .htaccess apache)

Widget Logic
This is a really nice Wordpress plugin that gives every widget an extra control field called "Widget logic" that lets you control the pages that the widget will appear on.
(tags: wordpress widget plugin sidebar)

Multiple Category Selection Widget
Turn your Wordpress post categories into a search powerhouse! This plugin gives you the ability to provide your users with a widget full of dropdowns based upon parent categories and their sub-categories.
(tags: wordpress plugin search)