Arc is underrated as an information management tool. There's something to be said for having a web framework that works out of the box. Rails is probably the only other framework that makes it as easy to "just make some forms that pass data around and run some code on that data." But not quite -- I haven't seen arc's closure-storing technique used in any other web framework. The main issue that arc solves is that it…
Some arc code I wrote back in the day, for generating textual descriptions from structured data using a web frontend, is still in production at a previous company of mine (as far as I know). It was indeed a useful tool. It's a shame arc didn't have persistent data structures (besides alists :-) and a native hashmap type though. For those confused, we're talking about this: http://www.paulgraham.com/arc.html
You are in a CONS cell. The there is a CAR to the left, leading off to another CONS, and a CDR to the right, containing NIL. The garbage collector briefly enters the CONS, marks it, quickly glances at the NIL in the CDR, smiles quietly to itself, and looking relieved, hurriedly sweeps away through the CAR.
>GIVE CONS TO CDR
You give the CONS cell to its CDR, creating a circular list.