ChaiScript - Easy to use scripting for C++
chaiscript.com
chaiscript.com
This did not really give me any feel for whether I would want it embedded in my project or not.
Didn't do much to convince me. I'll stick with Javascript (QtScript really; which is insanely easy to integrate into a C++ Qt project) and Lua (with the excellent LuaJIT) for my embeddable language needs.
See: http://en.wikipedia.org/wiki/QtScript
Obviously, Qt script is designed for c++ plus Qt whereas this is designed for c++ plus Boost. I personally think Boost is over-complicated ridiculousness but maybe that's just me. Still, there is at least one alternative to Chaiscript, if not more.
Looks cool.
A key weakness I see here is the lack of a standard library for Chaiscript.
If I choose to use my preferred approach of Swig+(C++)+Tcl, I get a command line REPL shell and Tcl's excellent file I/O stuff, regex, string functions etc for free (the Tcl pieces I mentioned are never the efficiency bottlenecks in the sort of compute-intensive programs I write).
I don't see enough here to convince me that it's better than pure C++ or swig+scripting language.