“HaloScan provides a free, easy to use commenting and trackback service for weblogs and websites, allowing visitors to leave feedback, share their opinion, or comment on the subject at hand.”
Basically, When you set up your blog in iWeb, you insert a small bit of text into the page. Then, you run your iWeb blog through iComment, and it converts that bit of text into links, compatible with Haloscan. You can find more information here. I haven’t tried it personally, but it seems pretty straight forward. Oh, and did I mention… it’s free! Well done Chad!