I feel your limitations are overridden:
small enough to understand, enough to show most of the (c) lisp tricks and functions without an opaque (“well-written” part desire), and independently of other packages.
Generic Lisp is a huge language, and the power set that comes up when combining language elements is much larger. You cannot have a small program showing "most tricks" in the CL.
There are also many concepts that you will find a stranger when you learn CL coming from another language. Since CL is less about tricks, but more about its fundamental paradigms.
My suggestion is to read it first and then start creating your own programs or looking into open source.
, , . http://www.weitz.de/.
PCL.:)