Plump is a parser for HTML/XML like documents, focusing on being lenient towards invalid markup. It can handle things like invalid attributes, bad closing tag order, unencoded entities, inexistent tag types, self-closing tags and so on. It parses documents to a class representation and offers a small set of DOM functions to manipulate it. You are free to change it to parse to your own classes though.
The project can be found on github including a fully documented symbol index and a getting started tutorial.
As of April 2014, Plump is available on Quicklisp.
Plump is licensed under the Artistic License 2.0.
XML HTML HTML parser