Ultimate Category Excluder allows you to quickly and easily exclude categories from your front page, archives, feeds, and search results.
Exclude pages, tags, links & categories by un checking the the "Display on your web site" checkbox, Use an excluded Tag to exclude Posts
Pro Categories Widget plugin.You have choice to specific categories exclude.
Display posts with category exclusions; select number of posts, post status, and post order.
Allows website visitors to deselect categories they don't want to see on your blog.