Performance and Types in Lisp takes a look at how SBCL handles types, particularly with type inference and use of declarations. It prompted some followup discussion on /r/lisp.
Butler is a Common Lisp kernel for IPython Notebook, but "don't expect anything to happen yet until more messages and sockets are set up." Pull requests welcome.
cl-lockable provides a simple locking mixin class with convenient macros and functions to work with it.