1. Doug Hoyte's book Let Over Lambda, chapter 6.3 Alet and Finite State Machines, raised my macrology to a new level. I used his ideas to implement a full-blown hierarchical state machine macro(s) (roughly 200 lines of CL, too large to post here). The hierarchical state machine paradigm is great for programming reactive things, e.g. gui's, hardware controllers, etc.
2. On Lisp's and PAIP's prolog compiler macros. The code itself is a nice brain stretcher. I use cl prolog to parse difficult languages (e.g. diagram-based languages).
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