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: http://sparkcapital.com/jobs/

Includes job openings from Twitter, Tumblr, OMGPOP and other popular web services. Please feel free to ping me directly with questions: andrew@sparkcapital.com, but know that Im not the hiring manager for any of these positions.