404 Notifier helps you identify any broken links in your site. Great if you move posts around and need to update links. Note it only works with pretty permalinks (2006/12/30/post-name), not ugly (?p123) ones.
Redirection Manage 301 redirections, keep track of 404 errors, and generally tidy up any loose ends your site may have. This is particularly useful if you are migrating pages from an old website, or are changing the directory of your WordPress installation.
AWSOM Pixgallery an Image Gallery/Archive plugin designed to make it easier for Artists or Webcomic creators to set up a portfolio of their artwork.
NextGEN Gallery a Gallery plugin using jQuery and Web2.0 features.
WPAds is a WordPress plugin for showing and rotating ads in your blog. You only have to define the ad positions and the ads you want to rotate in each position, and WPAds will serve your ads randomly. WPAds can show contextual ads (ie, Google AdSense, Yahoo Publishers Network, etc) and also image banners.
WP Plugins Tracker This plugin helps webmasters to track new releases of the plugins they are using in their website from their admin panel.
FireStats is a very detailed web statistics system