ILISP is a package that is designed to integrate various Lisp implementations (mostly Common Lisp systems and various Scheme dialects, including Guile) within Emacs (or XEmacs). ILISP runs an inferior Lisp process (in Emacs parlance) and provides a specialized set of commands, key bindings, and menus to ease the interaction with it. ILISP commands access the underlying Lisp process and provide ways to make the editing, compilation, and execution of Lisp programs much easier.
CL-PPCRE is a portable regular expression library for Common Lisp. It is compatible with Perl, and it's fast, portable (strictly ANSI-compliant), and thread-safe. It comes with convenient features like a SPLIT function, a couple of DO-like loop constructs, and a regex-based APROPOS feature similar to the one found in Emacs. In addition to specifying regular expressions as strings like in Perl, you can also use S-expressions which are more Lisp-y.
HTML-TEMPLATE is a portable library for Common Lisp that can be used to fill templates with arbitrary (string) values at runtime. It is intended to be used for HTML and is loosely modeled after the HTML::Template Perl module. It translates templates into efficient closures that can be re-used as often as needed, and uses an intelligent cache mechanism that allows templates to be updated while your program is running.
CL-INTERPOL is a library for Common Lisp which modifies the reader so that you can have interpolation within strings, similar to Perl or Unix Shell scripts. It also provides various ways to insert arbitrary characters into literal strings even if your editor/IDE doesn't support them.
HO-CVS is a version control system based on MetaCVS. In addition to the features of MetaCVS, it features module level versioning, the ability to reference every version (since there is a tag after every commit, which is extremely useful but slow), complex versions like #v1.2.3 designed to carry information about the change, operation hooks, and a somewhat powerful log command.