The main branch is Lisp, Lisp 1.5, MacLisp, Lisp Machine Lisp, Common Lisp. The evolution of that branch is now more in libraries and with individual implementations. It also got excellent implementations where all the low-hanging fruit is gone (Means easy improvements are no longer possible). For the community it is more difficult to improve the SBCL compiler, because it is already a substantial Lisp program. Still, if you look at the repository quite a few people add improvements to it.

There is Scheme, where there is still some research and evolution going on. See the work on R7RS and implementations like Racket.