CMUCL is basically a worse version of SBCL. SBCL is a fork of CMUCL with the goal of being more maintainable. Some things have been backported between the two, and there maybe a few things present in CMUCL that aren't in SBCL, but I think most of the interesting things have been added back in.
Clasp is to C++ like what ABCL is to Java. I haven't done much more that fire it up to see if it would run, but it's C++ integration looks fantastic.
CMUCL is basically a worse version of SBCL. SBCL is a fork of CMUCL with the goal of being more maintainable. Some things have been backported between the two, and there maybe a few things present in CMUCL that aren't in SBCL, but I think most of the interesting things have been added back in.
Clasp is to C++ like what ABCL is to Java. I haven't done much more that fire it up to see if it would run, but it's C++ integration looks fantastic.