Quanitity of listing is useless. What counts is consumer attention,
which is dominated by the top dozen or so indexes (Yahoo, AltaVista,
Excite, ...), which are all free. Who care's if some podunk index
lists you or not if nobody looks there?
Seems to me, the best strategy is a little simple elbow grease. Sit
down at each of the big indexes, look for subjects related to you,
and send mail to whatever lists you find. If you can't find them on
the first pass, they don't matter; and if those 500 lists aren't the
ones found on a related-subject search, they don't matter either.
Also--and this is an important underappreciated matter--keep your
HTML clean and searchable. Make sure your headers are actually
in header tags, that you include appropriate keyword METAs, that all
text is entered as actual text and not just graphics, that all the
graphics have ALT tags, that you don't play tricks like capitalizing
words like "<font size=+1>E<font size=-1>xtropy", etc. Things like
that make it harder for search engines to find keywords and index you
appropriately. In other words, write to the medium: HTML is a language
of content and structure, not appearance and style. You need style as
well, of course, and that's what style sheets are for. Unfortunately
the big two browsers don't yet correctly support style sheets (IE 3.0
supports most of it, Netscape not at all), so you'll have to do some
embedded style work until Netscape gets off their ass and does it
right, but you can still be kind to the robots without sacrificing too
much style.