The Rose main reading room of the NYPL Schwarzman building (that's the one with the lions) is quiet, has wifi and outlets, and is inspirational.
http://www.nypl.org/locations/schwarzman/general-research-di...
http://www.nypl.org/locations/schwarzman/general-research-di...
Before I joined the library, I'd come here all the time just to get work done. Now I come here to work.
Anyway, if you go a few blocks south to the Science, Industry, and Business Library (34th & Madison Ave) there's access to tons of market research databases that have helped fill out many of my friends pitch decks.