iLast.Fm provides a complete integration between your blog and your Last.fm account. It allows you to show what music you are listening to, your top albums, top artists, loved tracks, etc. on your blog.
WP-Cumulus allows you to display your site’s tags, categories, even or both using a Flash movie, rotating them in a 3D configuration. It works just like a regular tags cloud, but is more visually appealing. Clicking the tags can be a little hard (depending on your speed setting) but does take you to the appropriate page.
Actionable allows the creation of a categorized list of action items for users to check off and track. It was originally developed for Share 350.0 - a plan for regional sustainability to help people track their actions and efforts to create a sustainable community.
Allows you to create a link to domain.com/?random which will redirect users to a random post on your blog, in a StumbleUpon-like fashion. You can also specific in the URL random_post_type or random_cat_id. Created by Matt Mullenweg, himself.
This plugin automatically takes your oldest post, and updates its time stamp so that it appears as the latest post on your WordPress site. It does this by utilizing the cron feature built into WordPress 2.1 (and newer). It can rotate all the posts on your site, or just ones in a specific category. You can currently schedule it by setting the number of hours between shifts. For example, set it to 24 hours and it will shift the oldest post every day, at the time that you enabled it.
FLIR is similar to sIFR, but it uses images instead of Flash. Sure enough, someone has created a plugin to use FLIR with WordPress.
Do you have any cool plugins that you’d like to share? Let us know in the comments.