Chicken is an implementation of SchemeLanguage that's inspired by CheneyOnTheMta. It's maintained by felix winkelmann.
It's a Scheme-to-C compiler, but it's got an interpreter as well. It's got an easy-to-use FFI.

''Even if Chicken sucked, and it definitely doesn't, it would rock. Because it has felix. -- SunnanFenderson''

It's available at http://www.call-with-current-continuation.org.
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CategoryScheme