YouTube plugin - Insert YouTube.com hosted videos into a blog post.
b2media - Easily add images and links for Amazon products.
Democracy Poll - Add a poll to your blog sidebar.
Star Rating Plugin - Let users rate your posts by clicking on stars.
Sideblog - Display another blog in your sidebar.
Most comments - Add a list of posts with the most comments in your sidebar.
Bookmarklet 2 - An alternate version of the stock bookmarklet plugin that adds the link to the body of the post rather than the Link to Url field.