Summary
Considering how much time is spent in WordPress's back office, it's worth the time to make it as easy, effective, and pretty as possible. We should all shake the hand of every developer who spends time building these non-public facing plugins that make our lives so much easier.
Fluency Admin—Making your WordPress administrator beautiful and usable
StatPress—Tracking every step of a visitor's experience on your blog
404 Notifier—Keeping track of missing pages
Shockingly Big IE6 Warning—Helping those who are internet-challenged
Admin Links Widget—Quick access to select admin links from anywhere on your site
WordPress Admin Bar—Quick access to every admin link from anywhere on your site
Code Editor—Desktop-like code editing directly in your browser
WordPress Admin QuickMenu—Quick access to external websites directly from your menu
Broken Link Checker—Validates that all URLs on your website actually go somewhere
Email Users—Send mass e-mails to users and groups
Admin Management Xtended—Adds powerful...