BlogSpeak is a free remote commenting system for Blogger based weblogs. It gives those without the option to upload their own files  or access to scripting languages the ability to add commenting to their weblogs without the need to upgrade their current service.
$: Free
W: www.bighar.com/blogspeak/

Ehsany.tk is a Canadian site with a number of attractive templates for use with Blogger and Blogsky blogs. In addition to English language templates, Ehsan also provides several Persian templates.
$: Free
W: www.ehsany.tk

These little buttons are a favourite among bloggers and a good way to get others to link to your site. The online button maker is free and relatively easy to use.
$: Free
W: http://kalsey.com/tools/buttonmaker/

SquawkBox.tv offers a free basic commenting system with an upgraded version available for GBP £14/year. The upgrades include things like email notification, RSS support, banning of IP addresses and more.
$: Free; Upgraded: GBP £14/year
W: www.squawkbox.tv

From the UK comes Enatation offering basic free service with enhanced features available to supporters who make a $14 donation. The upgraded version shares a server with fewer accounts, has email notification and XML and CSV export of comments for archiving.
$: Free; Upgraded: USD $14
W: www.enetation.co.uk

HaloScan provides a free, easy to use commenting system for web logs and websites, allowing visitors to leave instant feedback. Basic version is free, value-added premium version includes several upgrades including a fully customizable template and email notification of comments on your blog.
$: Free; Premium version: USD $10/year donation.
W: www.haloscan.com

Launching in Summer 2003, the long-awaited "hosted version of MovableType" began taking "pre-registrations" on August 4th. TypePad has most of what MT has and more. This is a feature-packed solution designed to serve the needs of serious bloggers.
$: $4.95 to $14.95
W: www.typepad.com

Recently acquired by Google, Blogger is an easy solution for beginners and technophobes. All configuration and editing is done through a web interface. The free version carries a Blogger/Blogspot banner at the top of the page. At the time of this writing, details about the upgraded “pro” version were unavailable due to “retooling.”
Update: That retooling led to a single tier, free service that incorporates most of the upgrades which were previously available at extra charge.
$: Free service hosted with banner ad. USD $15 /year removes ad.
W: www.blogger.com

As you might expect, Radio offers a bit more functionality than free services such as Blogger. With Radio, you download a program to your computer and do all of your composing and editing locally. After you’ve edited, you publish your new content to your site. Radio Userland has an agreement with The New York Times which allows users to post NYT headlines and stories on their blogs at no charge.
A 30 day trial is available.
$: $39.95 US/year.
W: radio.userland.com

LiveJournal blogs can be edited either by using a downloadable program, like Radio, or by logging into your account like Blogger. Much emphasis is placed on the ‘community’ aspect of the service. The system is described as ‘open source’ and improvements to the core functionality are encouraged. The basic service is free. Upgraded paid accounts are available with extras such as @livejournal.com email addresses, friendlier domain names and faster server access.
Noticeably absent was an RSS feature.
$: Free basic service; $ 25 US/year upgraded service.
W: www.livejournal.com

Xanga works through a web interface, like Blogger. The free version is fairly bare bones but the upgraded version includes a rich text editor, image hosting, ability to post by email, etc. No RSS feature. The service is quite popular with teens and university students who refer to their blogs as their “xangas”. Reliability seems like it might be an issue. When I was writing this, the main site (and all blogs) were offline for a few hours while they tried to deal with a denial of service attack.
$: Free basic service; $ 25 US/year upgraded service.
W: www.xanga.com

Used by many of the most popular bloggers, Movable Type has about everything one could ask for. Implementing MT, however, means that a few technical hurdles must be leaped. Since it is not a hosted service, like Blogger or LiveJournal, you’ll need to arrange for hosting from a conventional hosting provider. Make sure you get a Unix host. Setting up Movable Type on a Windows server is the next thing to impossible. In the works from Movable Type developers, SixApart, is TypePad a hosted version of the blog software.
$: Personal use: free; business use: $150 US
W: www.movabletype.org/

Like Movable Type, Greymatter is free and quite full-featured. Also like MT, GM is technically challenging. While the support message board seems very active, many, if not most, of the sites listed on the Site List have either ceased to exist or moved to Movable Type.
$: Free
W: noahgrey.com/greysoft