If you do choose how-tos, I meant to say that the first place to mine should be this very list. For instance, a question the other day on seeding random sequences sparked an illuminating and far-reaching discussion.
Some things that make this list a great source:
* Extracting how-tos from the mailing list does a real service -- questions on the mailing list are much less visible via Google search than SO questions
* Answers here are likely to be deep and interesting (i.e., not simply answers you'll find in the docs)
* We own the list; no doubts about usage rights
* We have authoritative answers from code authors
Mining only this list would not be enough for a proposal, however; there'd need to be something else as well (e.g., mining SO/Reddit).
On the subject of mining SO, I'd suggest not only weighting by frequency but also searching out answers that came from the community -- e.g. Robert Kern, Warren Weckesser, Jaime Fernández del Río (jaime), and others whom I apologize for missing. Here again we'd add value by giving prominence (and an imprimatur) to the best answers.