A plugin that includes all of the main functions that theme authors frequently include in their themes, which don't belong there.
For too long, themes have been building functionality into their themes that really doesn't belong there, such as setting favicons, and adding Google Analytics code. This plugin moves that functionality into a plugin, where it is portable, should you change your theme.
This plugin is still very much in beta and in development, but I'm looking for input from you as well. What functions have you seen in themes that don't belong there? Please tell me so that I can include them in future versions of this plugin. Please either send me an email or get in touch on Twitter.
I also run Do It With WordPress, which has an array of tutorials for managing, modifying and maintaining your WordPress sites, as well as The WP Butler, a service for keeping your site maintained, backup up, updated and secure.