First off, big thanks to Findinglisp for updating phpbb to the latest version. Spam levels are *way* down.
Also nice: The site now has Atom feeds; so you can check for updates without actually visiting the site.
You can subscribe to feeds for the whole site or for individual forums. These do not require an account login. In most browsers, an RSS indicator will appear on pages with an associated feed. The Moz team, in their infinite wisdom, removed this indicator after Firefox 4; but there are many RSS add-ons for those of us stuck in the mud. (Firefox 10 does have feed subscription under the Bookmarks menu.)
The top-level feed is http://lispforum.com/feed.php
The CL feed is http://lispforum.com/feed.php?f=2
The Scheme feed is http://lispforum.com/feed.php?f=22