Victoria and Albert Museum - London
History of Theatre Posters and Links to the examples in their collection
http://www.vam.ac.uk/content/articles/t/theatre-posters/
Public Theatre Posters - Paula Scher and Pentagram Design Studio
http://designarchives.aiga.org/#/entries/%2Bid%3A2910/_/detail/relevance/asc/0/7/2910/the-joseph-papp-public-theater-poster-series-simpatico-him-merchant-of-venice-and-some-people/1
Voice Design - Adelaide
State Theatre Company
http://www.voicedesign.net/#/work/311
http://issuu.com/statetheatresa/docs/2013season-brochure
Frost design - Sydney
http://frostdesign.com.au/
By the way...Public Theatre is also an organisation in New York
http://www.publictheater.org/