Websites which you have also visited their physical headquarters:
Google (I stole a stick in Mountain View and gave a talk in NYC). ‎- Meg Vmeg
Audubon ‎- John B.
@meg At first I pictured a USB stick, then I thought no must be a tree branch, then some part of my brain said what this is google the USB thing could really be it. But now I'm back to the natural world mind picture. ‎- Micah
Yeah, natural sticks from stick trees. It took a while because I was limited to medians in the parking lot. For a talk at the Computer History Museum in...2011? Top 3 museums ever. ‎- Meg Vmeg
I'd really like to go to that museum, actually. ‎- Micah
@John in Manhattan? ‎- Micah
I haven't even visited where I work, never mind anywhere else. ‎- April
I worked for a web hosting company for a while so I was in the building with Martha Stewart's servers, among others, but I guess that's not what you mean. ‎- Christina Pikas
Soundcloud, textr, wire, teleport, kayak, wimdu, just to name the first I can remember. But surely a lot more of them ‎- fewdayslate
mailchimp ‎- ellbeecee
@micah: No, the one in DC (which I guess might be their policy office) ‎- John B.
WebMD's Ny Offices (granted, i was working there) ‎- hedgielib
Christina, I'm gonna count that. ‎- Micah
CNET, Ask Jeeves, Apple, Google ‎- Spidra Webster
Mokum.place :pokerface: ‎- псы в рапиде
Google Russia, Booking.com. If we count the ones we work for - then plus utro.ru, yandex.ru, aeroflot.ru. ‎- убедительная докторская фантазия
@squadette: Hee hee! ‎- Spidra Webster
Nokia , u-blox, (long list of smaller companies I can't recall name) ‎- silpol
mokum :) ‎- radio me.fm
Not solely a website, nor started as one, but CNN ‎- ellbeecee