Pierogi : a revered artist-run gallery on the Lower East Side of Manhattan with a rich collection of flatfile work viewable in person or via their website.
Geoform.net : an extensive site of geometric abstraction organized by artist Julie Karabenick.
Vasari21 : a weekly newsletter/blog that features and introduces a range of artists. Developed and tended by writer Ann Landi.
Op-Art UK : a site dedicated to optical oriented work.