Bld-maxima-pkg is a project mainly written in Common Lisp, it's free.
System that loads Maxima into Common Lisp, and provides simplification of Lisp math expressions
Package to use Maxima as a package within Common Lisp.
Steps required:
Download Maxima source code
Follow the Lisp-only build instructions in INSTALL.lisp for the Lisp you will use this package with.
Edit the paths in the "eval-when" form at the top of maxima-pkg.lisp to point to the corresponding Maxima source files.
Load & use. If there's a problem with exhausted control stack (encountered on Win32 SBCL), try to restart and load again.
The primary function of this system is SIMP, which takes a Lisp mathematical formula, converts it to Maxima's internal Lisp form, and simplifies it, then converts back to a Lisp code form. Functions/macros unrecognized as math forms are left untouched.