Here, and discussed at Daily Nous.
The consensus in the comments seems to be that although the poster is beautiful – which it is – it would be good to include at least some women.
I would suggest that a poster with a lot of women would be even nicer, and here’s one good place to find them.
The poster’s creator cites two sources: The Internet Encyclopedia of Philosophy and the Stanford Encyclopedia. It’s not clear to me that either of these are doing the best possible job in documenting the existence of women in the history of philosophy.
Feminist History of Philosophy 
I just checked many of the links of Dr. Kate Lindemann’s Women of Philosophy page. Unfortunately, many are not working. I sure hope it is the time (Thursday 10/2/14 @11:30 a.m.) and not that the site is no longer maintained!
I’ve just clicked on a bunch of them and they seemed fine. The page moved recently, and is hosted by the Society for the Study of Women Philosophers. If you still can’t get in later you should get in touch atsswpdues@gmail.com
It seems to me that many of the links (or one big link) go to http://www.sswp.org.html but the address is http://www.sswp.org.
Thanks Matt! the link you suggested worked.
Pingback: The History of Philosophy as a giant poster, but without women (again). | Feminist Philosophers