xterm-extras.el is a package to allow you to use all sorts of modified function keys and other odd keys when running emacs with the -nw option. It requires a fairly up-to-date xterm; see the comments for details and other caveats. It has only been tested with a fairly recent CVS checkout of GNU emacs.
Package is unusable from the above web-site. Two necessary links are broken and xterm-extras.el is garbled.
The file is not garbled, it is just gzipped but does not have proper extension. Download it, rename to xterm-extras.el.gz, then gunzip. The content of the two files - Xresources and .inputrc is in the comments section in the beginning of xterm-extras.el so nothing is lost.