I've heard CL is famous for having advanced libraries and language features decades before other languages get them.

What are some interesting libraries or language features developed since 2005 that haven't yet made their way to other languages? Not a simple "Do X" library that a C programmer could easily copy, but something more like CLOS, contracts, or pattern matching that are cross-cutting.

It adds static typing to Common Lisp, while (I believe) still allowing one to escape to the dynamic world when needed. Sure, there are statically-typed languages, but I don't know of another dynamic language in which something like Coalton has been done.