I'm wondering what primers/guides/lessons/etc. are available for understanding how to rewrite Web addresses using Apache/.htaccess? Where is a great starting point?

My primary interest rates are finding out how to point certain sites to others, and just how to make use of servings of a URL as parameters to some script (i.e. "/some/subdirs/like/this" => "script.php?a=some&b=subdirs&c=like&d=this").

The Apache Documentation site includes a good summary of using mod_rewrite.

It covers the way the directive works and it has a number of good examples, eg:

RewriteRule ^/games.* /usr/local/games/web

RewriteRule ^/product/(.*)/view$ /var/web/productdb/$1

It coveres from the fundamental sytanx for altering the URI (that is that which you appeared to become asking about) in addition to using regular expressions, conditions and reacting with redirects.

The apache documents will always be helpful in my experience. O'Reilly's Apache: The Definitive Guide is another good physical resource.

Wrong with the manual?

The Apache manual is loaded with lots of good examples.