There is little chance the Standard is gonna get updated again, especially since CDR (the Common Lisp Directory Repository) kinda stopped. That said there are a few libraries that are kinda considered to be the default go-tos for various needs:
CL-PPCRE for regular expressions.
Bordeaux-threads for threads.
Alexandria for various miscellaneous stuff.
Trivia for pattern matching.
CFFI for, well, FFI.
And Series for functional iterative sequence-like data structures.
There's also ASDF and UIOP, but I'm not sure whether or not they're part of the Standard.
CL-PPCRE for regular expressions.
Bordeaux-threads for threads.
Alexandria for various miscellaneous stuff.
Trivia for pattern matching.
CFFI for, well, FFI.
And Series for functional iterative sequence-like data structures.
There's also ASDF and UIOP, but I'm not sure whether or not they're part of the Standard.