Libxslt is a C library for GNOME which allows developers to work with XSLT. It is based on libxml for XML parsing, tree manipulation, and XPath support. Also included is 'xsltproc', a command line XSLT processor. The library is written in plain C, making as few assumptions as possible, and sticking closely to ANSI C/POSIX for easy embedding. It should work on Linux, Unix, and Windows. Though not designed primarily with performances in mind, libxslt seems to be a relatively fast processor. It also include full support for the EXSLT set of extension functions as well as some common extensions present in other XSLT engines.
oXygen is an XML editor that supports any XML document, and works with XML Schemas, DTDs, Relax NG schemas, and NRL Schemas. It has powerful transformation support that allows you to edit XSLT and XSL-FO documents and to obtain documents in the desired output format (such as HTML, PS, or PDF) with just one click. It also includes a complete Subversion client, support for flattening XML Schemata, an XML Schema instance generator, integration with the X-Hive/DB, MarkLogic and TigerLogic XML databases, editing actions on the diagram, and a rename refactoring action.
FleXML reads a DTD (Document Type Definition) describing the format of XML documents and produces a validating XML processor with an interface to support XML applications. Because the DTD is known in advance, the C code generated is much more efficient than equivalent code using an API such as SAX.
uni2ascii and ascii2uni provide conversion in both directions between UTF-8 Unicode and more than thirty 7-bit ASCII equivalents, including RFC 2396 URI format and RFC 2045 Quoted Printable format, the representations used in HTML, SGML, XML, OOXML, the Unicode standard, Rich Text Format, POSIX portable charmaps, POSIX locale specifications, and Apache log files. It can also convert between the escapes used for Unicode in languages such as Ada, C, Common Lisp, Java, Pascal, Perl, Postscript, Python, Scheme, and Tcl.