I am a member of the International Association of Astronomical Artists. You can also check out some of these related links:

Novagraphics Gallery. The world's first and largest gallery devoted to space art.

Chesley Bonestell Art Gallery
The Chris Butler Space Art Gallery
Jim Scotti's (mostly space) art page

A group photo of some IAAA artists at the grand opening of the new Novagraphics Gallery (May 10, 1997).

Some photos from the IAAA's Arches Workshop.

Some photos from the IAAA's Death Valley 2005 Workshop.