Current members are:

Sponsored by HGTV and Co-presented by the American Poster Institute (API) and SXSW, Flatstock 33 will display the works of more than 100 artists from across North America and the globe. The exhibition is free and open-to-the-public running March 14-17 2012 and features posters representing decades of styles, colors and techniques for sale. Show up early and be ready to be overwhelmed with amazing posters. (You might want to bring some dough since you won't want to leave empty handed!) The exhibition is free and open to the public.

"Every March, thousands of young, jeans-wearing techies, filmmakers and musicians descend upon Austin, Texas, harboring dreams of getting noticed and hitting it big. They come not just for the balmy weather or the Tex-Mex food but for South by Southwest, a collection of conferences and festivals that's considered one of the most influential happenings on the annual cultural calendar." -- CNN, March 10, 2011

UKPA
The UKPA (UK Poster Association) is an umbrella organization created to help support and promote the work of UK poster artists.
The UKPA is an organising body and web resource set up to promote the UK gig poster scene, with a focus on limited edition, screenprinted works. The UK possesses a vast wealth of talent within the field of gig poster design that finds its roots in both the concert posters of Britain’s musical past as well its contemporary American counterparts. As the scene continues to grow this side of the pond, UKPA hopes to offer help and information about those working within it, how clients can go about commissioning work, as well as promoting and supporting exhibitions of these artists.