I stumbled across this page when I randomly surfed around on the web and think it's quite useful for all those of use who can never get enough cant words. While it doesn't have many of the words used in planescape cant, it's a dictionary of the real londoner thieves cant (or so it claims) which was the source of inspiration for the planescape material.
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Ah yes, this is the one I use. As a limey, I recognise at least some of the terms from knowledge of the period but can't speak for all of it. Certainly fun though.
For the expiation of more grandiose badinage, I'd recommend the later works of Jack Vance (or just the RPG, which is written in the same style).