eXist is a native XML database featuring efficient, index-based XQuery processing. It provides a complete ecosystem for building applications entirely based on XML, XQuery, and related standards. The high-performance XML database engine stores textual or binary data and documents without requiring a database schema. Using XML across all layers makes mapping technologies superfluous and increases productivity. A browser-based IDE and a standardized application packaging system help developers get started quickly.
BaseX is a light-weight, high-performance, and scalable XML database system and XPath/XQuery processor, including full support for the W3C Update and Full Text extensions. An interactive and user-friendly GUI frontend gives you great insight into large XML data instances. It is platform independent and works out of the box.
Xidel is a command line tool to download Web pages and extract data from them. It can download files over HTTP/S connections, follow redirections, links, or extracted values, and process local files. The data can be extracted using XPath 2.0, XQuery 1.0, and JSONiq expressions, CSS 3 selectors, and custom, pattern-matching templates that are like an annotated version of the processed page. The extracted values can then be exported as plain text/XML/HTML/JSON, or assigned to variables to be used in other extract expressions or be exported to the shell. There is also an online CGI service for testing.