HotSax
HotSAX is a fast, small footprint, non-validating SAX2 parser for HTML/XML/XHTML. It can be used in simple web agents, page scrapers, and spiders. It is similar to the Apache Xerces parser, except that it can generate SAX events for badly formatted HTML as well.

HTMLParser
HTMLParser - a super-fast real-time parser for real-world HTML. What has attracted most developers to HTMLParser has been its simplicity in design, speed and ability to handle streaming real-world html.

Java HTML Parser
HTML Parser that produces a stream of tag objects, which can be further parsed into a searchable tree structure.

Jericho HTML Parser
Jericho HTML Parser is a simple but powerful java library for parsing and modifying HTML documents, including analysis of abritrary HTML forms to determine the structure of submitted data.

JTidy
JTidy is a Java port of HTML Tidy, a HTML syntax checker and pretty printer. Like its non-Java cousin, JTidy can be used as a tool for cleaning up malformed and faulty HTML. In addition, JTidy provides a DOM interface to the document that is being processed, which effectively makes you able to use JTidy as a DOM parser for real-world HTML.

NekoHTML
NekoHTML is a simple HTML scanner and tag balancer that enables application programmers to parse HTML documents and access the information using standard XML interfaces. The parser can scan HTML files and "fix up" many common mistakes that human (and computer) authors make in writing HTML documents. NekoHTML adds missing parent elements; automatically closes elements with optional end tags; and can handle mismatched inline element tags.

TagSoup
TagSoup, a SAX-compliant parser written in Java that, instead of parsing well-formed or valid XML, parses HTML as it is found in the wild: nasty and brutish, though quite often far from short.