LastHalo - Add-On for Haloscan users to display the latest comments. - http://lasthalo.uzyn.com
PurpleBunny - Add your comments to the web page you are currently reading for others who come after you, and read comments from people who came before you. - http://www.purplebunny.com
Cbox - Scalable tagging and commenting system that lets visitors leave you messages and talk to each other. Premium version has live chat capability. - http://cbox.ws
Blogcomments - Free self-hosted commenting system with an ASP base. Layout can be customized using CSS. - http://www.noipo.org/index.php?id=4
Tara Star's Script - Requires PHP. Notifies the weblog's owner when new comments are posted. - http://old.climbtothestars.org/coding/comments/
Pollxn - A lightweight discussion engine for Blosxom and other weblog/blogging applications. It lets people post comments about your blog stories right on your site. - http://www.nukekiller.net/pollxn
ZonkBoard - A free blabber board made specifically with weblogs in mind. - http://www.zonkboard.com/
Reblogger - A comment system for weblogs that can be used as a remote commenting system or can be installed on any server with cgi capability and perl. - http://jsoft.ca/reblogger/
DotComments - Server-side, requires PHP. Has its own support email list. - http://groups.yahoo.com/group/dotcomments-support/files/
HaloScan - Free, easy to install weblog commenting system allowing webmasters to receive feedback on their website. - http://www.haloscan.com
YACCS - Free remotely-hosted commenting. Available in multiple languages and does not require JavaScript. Users can edit and delete posts, and ban IP addresses. - http://rateyourmusic.com/yaccs/
Tag-Board - Free message board for blog webmasters wanting to communicate with users. Displays inline comments. - http://www.tag-board.com/
BlogKomm - Free commenting script displays comments below posts rather than in pop-ups. - http://www.blogkomm.com