1. xarray
    This package implements a generalized interface for array-like
  2. XCL
    XCL is a Common lisp implementation featuring a kernel written in C++ and an optimizing compiler with backends for x86 and x86-64
  3. XCVB
    XCVB, an eXtensible Component Verifier and Builder for Lisp is an attempt to replace asdf
  4. xelf
    Xelf is a simple 2-D game engine for Common Lisp
  5. xgboost
    Common Lisp interface to XGBoost
  6. xhtmlgen
    xhtmlgen is an XHTML generator
  7. XHTMΛ
    XHTMΛ is yet another (X)HTML/XML manipulation library You can find it at common-lisp.net/project/xhtmlambda
  8. xindy
    xindy is an index processor that can be used to generate book-like indexes for arbitrary document preparation systems
  9. XIT
    A graphics toolkit from the University of Stuttgart which provides an object-based interface to the X11 window system, based on CLX and CLUE
  10. XL-Wiki
    XL-Wiki is a fork of CL-Wiki that aims to allow applications to modify and extend its functionality in interesting ways