A great article on compile-time computing (with CL): https://medium.com/@MartinCracauer/a-gentle-introduction-to-...

There are good references and snippets on the Cookbook: https://lispcookbook.github.io/cl-cookbook/

for libraries, see https://github.com/CodyReichert/awesome-cl (and see the lparallel or lfarm libraries, channels, cl-gserver, the built-in SBCL threading functions, etc)

Also note that CL is not purely functional, you can throw in FP or OOP or iterative code.