Ask HN: Are there any HN mashups?

A lot of precious jewels lie buried deep inside HN. A few tools like like Search YC, Ask HN, Hacker Monthly exist to bring that to the surface.

What other existing tools can you think of?

Are HN archives available anywhere for HN enthusiasts/arc hackers to slice and dice?

If someone wanted to create such tools, is it generally encouraged or discouraged?

Is there some particular tool you wished, was available to surface the content of HN?

Has PG ever discouraged or prevented HNers from creating such tools?