I've found two different toolsets for embedding a C/C++ interpreter into my own code. I haven't tested these yet, but will keep them in mind.
Ch is an embeddable C/C++ interpreter with some nifty extentions, and it parses and executes C code without transforming it into intermediate or byte code.
Ch supports ISO C standard (C90), major new features in C99, classes in C++, POSIX, X/Motif, Windows, OpenGL, ODBC, GTK+, C LAPACK, CGI, XML, 2D/3D graphical plotting, advanced numerical computing, and shell programming.
Ch Standard edition is free of charge.
At first glance, Ch looks a lot more comprehensive than CINT.