Companies that have been funded by Spark Capital (and thus are venture-backed and can afford market salaries) have all their aggregated open jobs listed in one place: <a href="http://sparkcapital.com/jobs/" >http://sparkcapital.com/jobs/</a>
Includes job openings from Twitter, Tumblr, OMGPOP and other popular web services.  Please feel free to ping me directly with questions: REDACTED_EMAIL, but know that Im not the hiring manager for any of these positions.
Ask HN: Who is Hiring? (March 2012)