Ch is a complete C interpreter that
supports all language features and
standard libraries of the ISO C90
Standard, but extends C with many
high-level features such as string
type and computational arrays as
first-class objects.
Ch standard is freeware but not open source. Only Ch professional has the plotting capabilities and other features one might want.
I've never looked at this before, but having a c interpreter on hand sounds very useful, and something I will likely add to my toolset. Thanks for the question!
Edit:
Just found out that one of my favorite compilers, TCC, will execute C scripts:
It also handles C script files (just
add the shebang line
"#!/usr/local/bin/tcc -run" to the
first line of your C source code file
on Linux to have it executed directly.
TCC can read C source code from
standard input when '-' is used in
place of 'infile'. Example:
the ROOT project provides a very functional C and C++ interpreter called Cint. I'm quite fond of it. It takes a little getting used to interpretively, though.
TCC is a very good choice as well, but i'm not able to vouch for its REPL
PicoC is a very small C interpreter for scripting. It was originally
written as the script language for a UAV's on-board flight system.
It's also very suitable for other robotic, embedded and non-embedded
applications.
The goal of the ccons project is to create an interactive console for the C programming language, similar to "python" and "irb" for Python and Ruby respectively. The project builds on top of clang and llvm.
CERN has a toolkit called ROOT, which is meant mainly for scientific or data analysis etc.. purposes but it has a Clang - based C/C++ Interpreter called Cling.
They were using a C interpreter called CINT before they adapted Cling. CINT is lightweight & still seems to be available for download.
I think you may get some other by carefully searching through Wikipedia list articles.