MarkTroll is a WordPress plugin that will let you shadowban (hellban) any unlogged (regular) commenter on your blog.
FeenBan is a WordPress plugin for shadowbanning / hellbanning commenters.
WP Ban Manager enables you to block ips and users from posting comments to your site
Extend Visitor Maps and Who's Online with extra features, such as IP and referer banning. Display the referring host name and search string.