Index of packages:
trivial-garbage provides a portable API to finalizers, weak hash-tables and weak pointers on all major implementations of the Common Lisp programming language. For a good introduction to these data-structures, have a look at Weak References: Data Types and Implementation by Bruno Haible.
Source code is available at github, which you are welcome to use for submitting patches and/or bug reports. Discussion takes place on trivial-garbage-devel at common-lisp.net.