Anyhow, after a bit of searching, it turns out that the guy who already solved this problem made a webapp called HitTail. It has the broad thrust of the features I wanted: tracks what queries get people to find you (unnecessary, I can do that already), and then selectively picks queries out which (the site claims) hit a cluster of snowflakes and are not currently very competitive.
by
hittail
2007-06-15 13:03
HitTail
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SEO
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business
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marketing
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online
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traffic
http://microisvjournal.wordpress.com/2007/05/30/ranking-for-an-arbitrary-organic-search-query/
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