This script can be directly used as a CGI script, except that you have to change the source to have your LJ username (instead of mine). The tag-name information is laid in PATH_INFO of the url. For example, to get entries tagged python, one can use this url. An entry is tagged with foo if either its "title" or "post-body" contains the term foo (case insensitive).
And of course, this can be used with feedburner, like mine.
This is cross-posted from my journal
Update: This script requires feedparser. It comes as a single script (feedparser.py), download it and put in the same directory where ljtagfeed.py is copied to.