Embedded scripting languages

What scripting language would you embed to a program? The performance would not be main issue, since the compiled part of the program would worry about that.

The scripting language would call many functions written in C, C++, or whatever lang that can compile C-like functions (so there needs to be some kind of easy to use FFI).

I thought about options here:
- Lua
- Scheme (tinyscheme or whatever)
- Something else?

Now, what would /prog/ use, and why? ("Read SICP" is not a valid answer here)

You should first ask yourself if you really need an embedded scripting language. If you don't need to expose scripting functionality to end users, then you'll probably be better served by keeping everything in C or C++ and at most using a higher level language for compile-time data generation. And think hard about that, because a lot of the reasons people give for including scripting support (like data entry) can be trivially solved without a complete programming language.