ECB is a source code browser for (x)emacs. It displays a couple of windows that can be used to browse directories, files, and file contents like methods and variables. It supports source code parsing for languages like Java, C, C++, Elisp, Scheme, Perl, TeX, LaTeX, etc. In addition, it offers an (optional) permanent "compile window" at the bottom of the emacs frame, which is used to display all help and compile output. The rest of the frame is called the "edit area", which can be divided into several edit windows that are used for editing the sources. Deleting some of the edit windows neither destroys the compile window nor the browsing windows. It requires the CEDET suite.
SLIME is an integrated development environment for Common LISP which does everything you would expect from an IDE: code evaluation, compilation, macro expansion, and auto-completion. It also finds definitions of functions, and marks LISP forms which the compiler finds to be erroneous. It provides easy access to implementation-specific online documentation as well as the ability to look up symbols in the ANSI Common Lisp HyperSpec. Further, it includes an interactive debugger and object inspector.
XSLT-process is a minor mode for (X)Emacs that allows you to run a Java XSLT processor on a buffer and display the result in another buffer, or in a browser. You can also run the XSLT processor in debugging mode, setup breakpoints, run step by step, view local and global XSLT variables, and many more.
xslide is a major mode for (X)Emacs for editing XSL Stylesheets. Its features include an XSL customization group for setting some variables; an initial stylesheet which is inserted into empty XSL buffers; a "template" menu for jumping to template rules, named templates, key declarations, and attribute-set declarations in the buffer; an "xsl-process" function that runs an XSL processor and collects the output; syntax highlighting; an "xsl-complete" function for inserting element and attribute names; an "xsl-insert-tag" function for inserting matching start- and end-tags; automatic completion of end-tags; automatic indenting of elements with user-definable indentation step; and a comprehensive abbreviations table.